My girlfriend's family wants me to be more formal.

What is your girlfriends view on this? What would you normally wear?

 

In my opinion people should just stop telling other people what to do, especially when the sole reason for doing so seems to be "What might people think???", or similar bs phrases that only serve to mask someone's own intolerance. Live and let live, is what I always say.

That being said, it really depends on how far you're willing to go to fulfill your girlfriend's families' expectations and on how comfortable you feel doing it.
Did you ever talk to them or to your girlfriend about the way their expectations make you feel?

 

I don't think it's unusual to ask that you are wearing nicer clothes for church. Some churches are a "come as you are" while others prefer a more dressed-up formality. When I used to attend church as a child, it was always "Sunday best" kind of clothing. If the congregation in general is wearing the type of clothing they are asking you to wear, then it's a reasonable request.

Why is this a big deal? If I was being invited to someone's event, why wouldn't it be reasonable to ask "What should I wear?" and wear what they suggest is appropriate to that event.