Well, sometimes it pains the parents because they want what is best for the child and think this is not what is best for them.
Sometimes it pains the parents because they see themselves living vicariously through their children infinitely and so they want their kids to live lives they approve of.
Sometimes it pains the parents because they think that other people’s opinions of them are based on how well they raised their perfect family.
It sounds like you get the feeling from your parents that it is one of the latter two reasons, and not the former. Unfortunately, that is quite common, and if you feel that way, it is probably true in your case.
The reason you should not do these things is NOT because it bothers your parents. Your job in life is not to make your parents happy; it is not to bring nachas to your parents; it is not to give them feelings of immortality and peer-recognition. Your job is to live your own life.
In living your own life, you certainly should take guidance from your parent’s values; if they think something is very important–it very well may be.
I personally think you should not be doing the activities you discuss, and I think so because I think doing so will hurt you in both the long and short run. I think you know how harmful it will be as far as your personal and family relationships, and the fact that you still want to do them says to me that there is some even stronger pain you think you will solve by doing them. I think you should speak to someone about that.