Netlify absolutely kills it with their entire suite of offerings. I highly highly recommend people try it out if they haven't yet.
Their free tier is probably too generous though. I know someone running the biggest website in a massive niche and they are serving their SPA for free from Netlify.
Your point stands nonetheless — they could certainly be losing money on certain large users of their free tier. Serving relatively static content has gotten extremely cheap across the board, though, and like the parent said, they might be benefiting from the pricing by more indirect means.