I had the same issue with one of my twin boys who just turned 6. He refused to wipe his own butt. He'd sit on the toilet and scream for us to wipe his butt and cry and cry for us. We kept telling him that he is old enough to wipe his own butt and he kept saying just a few more weeks. Then, when just a few more weeks went by, he kept telling us he'll do it when he turns 6.
He turned 6 in June and kept yelling for us to wipe his butt and this time we held him to it. I still had to go in the bathroom with him and hand him the paper for a week or so and remind him and show him again how to do it (he still does it all wrong but that will come in time). But when he would yell for us, we would say that we were in the middle of doing something and to hold tight and then we'll be up and make him wait extra long. We figured by a certain point he'd get bored of sitting there and realize how much fun he was missing, and do it himself. It worked over time. He still calls for us when his bowel movement is a little loose and I kind of get that is icky for him so I still go in the bathroom and talk him through it...
This is my same twin who is still in pull ups that are wet every single morning. I was going to wait until he turned 6 to address this issue head on- not sure what I'm going to do about that but I'm going to have a chat with his pediatrician and then maybe get one of those alarms. He really wants to be able to wear underpants to bed like his brother and I think he's over the age where that chemical kicks in.
It so ironic, because the other boy twin was so fastidious about using the potty at a young age and pretty much potty trained himself and hardly ever has nighttime pee accidents.