Who buys wedding parties attire?

My sisters are just as not well off as I am, so I made a nice gesture by getting their bridesmaid outfits. One sister took me lingerie shopping and graciously bought my needs, almost 1/3 the dress cost. Her husband did need a suit to match her, so I went with him to help him choose based on color, but he paid for his own suit as he isn’t part of the wedding party.
so it’s kind of whatever works.

Agree with what others have said. It's still the norm for the wedding party to buy their own attire. If you can afford to pay for them, I'm sure they'd appreciate it, but it is by no means expected or typical.

I do think its important to communicate expectations of your wedding party before they commit though because what is expected (and how much time and money is involved) can be drastically different from one wedding to another. My MOH is going to spend about as much to be in my wedding as any guest would because I'm letting her choose her dress (with a few rough guidelines around color, fabric, length), she can wear her own shoes and accessories, I don't expect/want a shower/bachelorette party, and we are going to have her stay with us in an AirBnB that we have paid for. On the contrary, my FH was the best man in a wedding and spent over $1000 to be involved because of attire, bachelor party, and resort lodging. It can vary greatly so being upfront with your party about what is expected is important.