Can i be shirtless all the time?

If you look like me, yes.

I was at the church with my mother-in-law and I saw a man who came to fetch his family bare chested. He was in his car but it seems so inappropriate.

If you're a woman, you can't.
If you're a dude, yes.
If you're a dude who happens to be on the heavier side, you can, but you risk others making fun of you. I say this because I've seen dudes on the heavier side get ridiculed for being shirtless.

Normal. I do it everyday

Sometimes, being too exposed can be too much for people to handle. Best to know when to have that shirt on.

Not normal usually.
Life threatening in winter.

Sign I saw in a bar: "No shirt, no shoes, no service for guys, free drinks for women."