My boyfriend says his family's daughters-in-law can't wear lowers and T-shirts. Am I overreacting?

So I casually asked my boyfriend if, after marriage, I'd be able to wear sweatpants and a T-shirt around the house the same way I do at my own home. He replied, "You can wear them, but the daughters-in-law in my family don't walk around in sweatpants and T-shirts."

When I asked why, he said it was because of family and social expectations.

The thing is, I don't want to argue with him about it because I know he grew up in that environment and probably sees it as normal. I also know I can't change his family's mindset.

But personally, I can't imagine being happy in an environment where what I wear in my own home is determined by the fact that I'm a daughter-in-law. I've seen the women in his family, and they seem comfortable with those traditions, but I don't think that lifestyle is for me.

I'm not asking whether his family is right or wrong. I'm wondering if this points to a deeper compatibility issue when it comes to values, personal freedom, and expectations around marriage.