New Muslim question...

I hang around with Muslims more nowadays; sometimes we go out for meals or get coffee or something, and I offer to pay. There's a range of reasons for doing so, partly just to be nice, partly to do a good deed, partly because [I'm kind of Chinese now](https://islam.stackexchange.com/questions/37158/does-he-who-imitates-any-people-is-one-of-them-mean-im-chinese) and it's a Chinese custom, and partly because of feminist beliefs. Sometimes it's because I've invited people out.

However, every time I've offered to buy a Muslim man a coffee or pay for a meal, he's awkwardly refused. Each time I've been given a strange look as if I've broken some kind of boundary. Basically, my question is *is this a Muslim thing?* Or, more formally:

**Question**: Is there an Islamic reason non-mahram Muslim men refuse to let me buy them e.g. coffee or a meal?

This has happened three times now. It's possible I'm reading too much into this, and this may be unproblematic in Islam, and just happened in those particular cases. It's possible it's impermissible and I'm unaware. Or maybe it's something along the lines of [hayaa](http://idealmuslimah.com/black-magic-evil-eye-a-jinn/41-character/modesty/328-hayaa-shyness.html) (shyness).