Why is three kids more difficult than two?

Let's be real: sometimes having three kids is actually a blessing.  The kiddos entertaining each other instead of always "needing" you to play with them.  Being forced to have a routine.  Positive reinforcement from another child. 
Sometimes...having three kids is hard. 
*I have only two hands.  So when I need to go out and do stuff with all three by myself, there's only so much I can keep a handle on.
*One kid often gets left out of games and such.  Which means when two are playing happily together, the one who's left out often ends up getting into extra mischief to try and get attention from you.
*Maybe it will be difference once they're older...but Hux is still rear facing (way, WAY safer) and has found that he gets a lot of [negative] attention by putting his feet in The Olders carspace.  Seriously, what can you do about that?  Close to nothing.
*When there are just two kids, it's relatively easy to find the balance if you have one who's an introvert and one who's an extrovert.  But when there are three, it's never enough for anyone.  And apparently throwing a third kid in the mix has turned my uber extroverted Gabriel into an uber touchy-homebody who just wants "to stay home and cuddle" all.the.time.
*The house.  It's seriously a wreck.  All the time.  I'm not exaggerating.  When there was just one kid, it was still relatively tidy.  If you don't pick up your toys before nap/bedtime, they got put in The Time Out bucket until the next day/whenever you're willing to put them away (which sometimes lasted for weeks).  When there are two kids, it's hard to balance because you're never totally sure who took out said toy.  Especially hard when your older kid gets upset that your younger kid is too young to help pick up/makes more of a mess "helping" than if he's already in bed.  This can usually be contained if you offer to help play The Cleanup Robot Song and help Older Kid pick up the toys since Younger Kid is already in bed and you want to be fair.  Whatev.  I can handle that (most days).  However...when there are three kids...EVEN when you try and have everyone put toys/books/whatever away right after they're done playing with it (before they can bring out another toy/book/whatever), it ends in disaster.  Because you can only watch so much.  No one will ever admit that they took out this, that, and the other toys without putting the first two things away before bringing out the third.  Everyone feels they're doing way more than the others in regards to cleaning up.  Even when you spend absurd quantities of energy trying to keep everything semi-decent (we aren't talking Rosie Homemaker clean, but merely non-tornado picked up) it still ends up a mess every.single.day.  [For someone who is an Acts of Service love language and who feels her life is a wreck when her home is a wreck, this is a real hurdle.]
*Your childless friends and friends with one kids who were still great when you had two little monsters...it changes.  It isn't always that *their* attitude changes.  Some friends are really great about it and are very helpful and understanding...but even with those great friends, it's hard not to see the total inequality when you're together with your hair and brain all frazzled and they're more or less put together.
*Finding someone to watch your kids (even for a couple of hours) is NOT an easy task.  I can say this from the Mother of Three point of view and the Come-On-Over-For-A-Playdate point of view.  Having one extra kid to your house more or less (depending on the kid and the aura of the night) can be WAY less work than having just your own kids.  Having two kids is often more work because, once again, someone often ends up feeling left out and/or you never know where everyone is located (your ears get more and more trained the more kids you have so this is less problematic).  But having three kids?  Let's think about this.  For those who have only one kid, that quandriples their normal kiddo time.  *swipes forehead*  For those who have two kids, there's more than double the crazy they're used to.  If you already have three or more kids, it's more or less just throw it all in there because it doesn't seem like much extra effort.  It's not IMPOSSIBLE to find a sitter, but trading babysitting is more difficult and finding a sitter (at a price you can afford) becomes increasingly difficult.
*Similar to the sitter: finding places and times to go out and do fun things get exponentially tougher the more kids you have.  Maybe it would be different if they were all the same age range and were on the same schedule.  But pretty much how it goes is: kids wake up at five (six if you're really crazy lucky), nowhere opens until eight...but by that point, you have three hours to cram everything you want done until you have to be back at the house (with lunch eaten) in order for quiet time to start.  What about after quiet time, you ask?  Yeah.  That's not a safe bet.  Sometimes everyone sleeps (although not at the same time, if it happens at all).  Sometimes no one sleeps.  Any which way, attitudes are generally worse for the wear after quiet time, whether a true rest was had or not.
*Couple time (linked to finding a sitter): it pretty much doesn't happen.  Rather...it does happen, but you have to be VERY cognizant about forcing it to happen...and when it does, it's hard to talk about anything other than just the kids (because they take up so much time and energy)
*Alone time: see above.  Alone time with true meditation is a total joke

Everything considered...I'm definitely of the opinion that adding a third for a couple of days is like an extra fun extra long playdate...but adding a third consistent kiddo into your life makes your life way, way more confusing/stressful/etc.  BUT...Total total honesty: I wouldn't change it for the world.

Also, fingers crossed that once Hubby is back home from his month-long job training, my life will get way easier.  Fingers crossed.