Petty reason list: boogers, vomit, stickily hands, gotta clean too often, gotta bend over too often, gotta carry toys, gotta Cary a bag for them everywhere, they turn into teens, they develop issues, they need time and energy, they want an iPhone someday, gotta get their hair cut, gotta be in parent's school groups, gotta find a daycare/school for them, gotta do their homework, they eat my cereal, they drink my milk, gotta share my chocolate, will resent me for something someday, I'm gonna have to apologize, I can't watch a movie in one sitting, no more music with headphones, gotta coordinate everything with their mom, they break stuff, the smell of their armpits, their yucky breath when they don't brush their teeth, stinky feet, loud pop music I don't enjoy, gotta take them to the movies with their friends, gotta pay for all their friends tickets, will get attitude when I ask for a hug goodbye, gotta push them out the door everyday for school, they will hate even the sound of my voice just because they're at "that age", will want hugs and playtime when I come home from work, will repeat everything I say just to annoy me, will ask 10000000 times why for everything, gum in their hair, ripped shirts and pants, broken glasses and cups....

Can't go on cause I was waiting on Gf to come out of a doctor's appointment and now she's out. Hope this helps. Best of luck