A question for the guys

I'm 38 years old and I've never worn a T-Shirt under a dress shirt until recently... like, the last three days. I've seen many guys wearing them and many guys not wearing them. My thought has always been that it's an extra layer and I sweat enough without them, thankyouverymuch. But I bought some and decided to see what the big deal is. I'm now on day three and I don't get it. It's not uncomfortable and doesn't seem to cause me to sweat any more than usual but I don't see a benefit.

I googled the question and all I can come up with is aesthetic reasons: because someone said it looked better.

So, why wear a t-shirt under a dress shirt?

Inquiring mind wants to know.