There are lots of practical reasons to practice Tai Chi - You can do it for physical health, for relaxation, for self defence, for... yadda, yadda, yadda ...
But, I'd like to mention something that I think often gets overlooked, it's enjoyable... You know, something that you can do without it doing any harm to anyone, and it's easy, and it can be done anywhere and (virtually) anytime. You don't need a lot of space, it doesn't make any noise, you can be wearing pretty much anything, you can do it for a few minutes or a few hours. It's YOUR decision what you do - it's your time to do something that is pleasant and makes you feel good.
Now, yes of course it will be relaxing and it will have the well-known health benefits so you get all of that too. But concentrate on the fact that you are simply doing something that you enjoy without any particular purpose and that is ABSOLUTELY your right.