that's a great question! broadly, I think it's an overkill for certain types of creators (say an Instagrammer or Twitch streamer) to launch a Patreon. Buy Me A Coffee is a far more casual and friendly way to accept contributions from your fans.
We also differentiate from Patreon in a lot of ways. For e.g., creators love that we're putting fans/supporters in the front-and-center (like Twitch), which also encourages more contributions.