Unfortunately there are so many people who are never taught how to clear up after themselves as children, so they really don't know how to do it,or have no inclination to do it as adults.
It makes my blood boil when parents refuse to let or teach their children to do household chores ("it's easier to do it myself" or "but they're children- they'll have enough of that to do when they're grown up")....all that does is create adults who don't have a clue how to look after themselves when they leave home....
My boyfriends brother is supposed to be going to uni this September and he was complaining the other week that his mum took too long to make him a cheese sandwich.
My boyfriend has had things done for him as well, his mum washes all his clothes etc but she takes money off him like he's a free bank, and sometimes she does have a cheek complaining that he's not done something when hes paying for her to sit on her bum all day.
When we go away on holiday I have had the whole "ok lets wash up then we can do XYZ" "I've just eaten" "Yes but they're easier to clean if they're done now and then it's all sorted for tomorrow" "hmn" "i'll start on it.." "no I'll do it"
Start clicker training him