Why Can't My Kids Just Clean Up Their Own Toys?

So here's my story. I'm a stay-at-home dad with two kids, ages 4 and 6. They're great kids, but man, do they leave their toys everywhere! I've tried everything: I've put labels on the toy boxes, set timers for clean-up time, even made up songs about putting away toys (yes, it was a thing). You'd think by now they'd be better at cleaning up after themselves. But nope, every day is the same, Legos in the hallway, stuffed animals all over their beds, and more than once I've found a toy car in the toilet. Now, you might be thinking, 'Well, they're kids, what do you expect?' And you know what? You'd be right. But here's the thing: I just get so frustrated sometimes that it feels like I'm doing all the work for them. The other day, I was going through my emails and the 4-year-old comes in with a truck. 'Daddy, can I put this here?' he asks innocently. Of course, I say yes, but now there's another toy right next to my keyboard where it wasn't before. And that's when I start thinking, is this normal? Am I the asshole for getting annoyed at something kids naturally do, or am I just stressed out from being a full-time parent and need a break more than they do? It feels like every day is Groundhog Day with toy clean-up, and yet I still expect it to be different somehow. So, what do you all think? Am I expecting too much here?