Do you find it weird that people wear band shirts of bands but they don't even listen to the band's music?

I don't think it's weird but it think it's not suit enough. Specially if they are aware of the meanings. We could have this moment where the person don't have any idea what he/she purchased is a particular logo or writing.

It's a usual psychology that what you wear speak about your personality and part of who you are. When you wear a band's symbolized cloths. It's expected that you know something about it. People will judge you by it. Maybe even a fan see someone with such shirt, in a random act they will approach the person to share ideas and communicate while they fail because the person know nothing.

(However, at the end, who cares ? Those people putting money in those band's pockets without even knowing if they worth it)

Personally, i prefer to wear something that i'm aware of it's meaning. I'm very caring about what's on it.