Interesting question about improvement. For me, I'm interested in improving my skiing for the sake of improvement, because I like a challenge - that's a piece of it. But a piece of it also has to do with stimulation. Sometimes I like a nice mellow ski. Sometimes I want a ski that will get my adrenaline cranking a bit, whether it's because it's a really challenging run, or because it's a less challenging run that I'm skiing with an increased amount of precision. That's a moving target, because the more I do challenging runs, the more challenging they have to be in order for me to find them challenging, and the better my skills need to be to handle them safely. Same with the precision. Sometimes I want to stop at the top of the run and pick my exact line and a particular speed before I drop in, and ski that exact line and maintain that consistent speed. This is pretty easy if it's a soft run, but if it's variable, or has a lot of ice on it, that demands better skills. The better my skills are, the more precise I expect that run to be. Also a moving target there. And then there's exposure to other skiers - I see a skier on the slope who is moving in a way I want to, or doing some trick and I'd like to, that's a call for improvement for me.
I don't think improvement is necessarily constant. I had some instruction recently, five or ten minutes of it, that caused me to hit a new level. I'd been at the same level of function for quite a while, not improving really, not trying to make a lot of changes or anything, but when this instruction came by it really spoke to me, and I found myself in a new state. I don't think it's constant, and I know it's not linear. So for people who don't have to be constantly improving, another question would have to be whether maintaining openness to improvement is important to their enjoyment of the activity.
Mr. S. is an advancing novice and has been for two years. He has a goal, which is to get down low-intermediate runs safely and have fun. Beyond that, he doesn't worry about it. He trundles down the novice runs, and he loves it. 90% of the runs I take scare the pants off him. He wants nothing to do with them. BUT...he's also a nordic skier, and an advanced one at that, and even though he's operating at a reasonably high level - he was skiing Trapp and Jackson last week - he's on the lookout for a downhill lesson because he thinks he can do a better job with them than he's already doing. So he enjoys his little plateau with alpine skiing, but wants to be constantly improving with nordic.