Bandcamp and Patreon serve artists at different scales. As a part-time musician who uses bandcamp for bands/solo projects, I much prefer the "single product" model (fans paying for a single track/ep/album as they choose) rather than an ongoing payment structure. I have zero illusions that I'm ever going to "get big" (read: support myself) from making music, so bandcamp allows me the opportunity to share my music and if fans choose to pay for it, great! I'd feel very uncomfortable soliciting recurring payment for something I do a few times per month.