it's not just about them not wanting you to play.. It's also about your general welfare.. Growing up is the time in which your body changes the most and in which you most easily develop agility and coordination. So it's only normal that they will want you to go outside and play basketball and/or baseball since this will help you to develop things that you will literally need every day: hand to eye coordination, balance, body coordination, orientation, stamina, posture, etc. Not to mention that you'll be outside, getting some sun (or rain
), building up your immune system, etc..
In addition to developing social skills from playing in a group and interacting with a group.. Though that is something you can (but necessarily always do) also develop with multiplayer games.
Besides spending too much time in front of a screen can have negative effect on your eyesight and posture. So I wouldn't recommend doing "just that" all day anyways.
Too much of one thing is never good. If all you do is play video games, they are right to restrict it and suggest you to also do other things. Why not try out a sport or spend some time with your friens (or dog or alone) exploring the neighbourhood. It's good for you and it can be fun. Your parents are trying to find a balance between what's good for you and what you enjoy. So they allow you to play computer games, but also want to see you go outside.