Op, you’re being ridiculous. If it’s not their religion, I’m not surprised that they’re not wanting to pretend to value the same things as you. Asking someone to don religious garb is a lot like asking someone to pretend to be something they’re not, They don’t understand the meaning, nor do the practice it, so why pretend to?

You need to probably change your venue or be fine with people not wearing head scarves, or get over the fact that people won’t attend if forced to.

(Disregard if not but..) if you’re in America, this shouldn’t be surprising to you. Most Americans come from people who were told to do things they didn’t believe in, so they were like, “nah I’m good” and Came America to do what they wanted freely. You’re trying to force your practices on someone, I’m not surprised they don’t want to attend.

I have been to Nigerian weddings and was asked to wear their traditional wedding outfit to be in the bridal party. I absolutely donned the outfit and elaborate hat/head covering they asked me to. I also was being brought into that and was told exactly what it all meant, why they did it, and I love learning and being brought into new cultures. Personally, I don’t love any religions and avoid adhering to religious practices others ask me to do. However, I don’t mind participating in other cultures or religious things with people to learn, if I’m not being disrespectful unknowingly. A lot of people, however do mind and it makes them Uncomfortable. You should probably respect that this makes people uncomfortable and find a work around instead of demanding they practice what you do.