What kinda adult would care about your ISP knowing you watch porn?

VPNs are often over blown. Their ads will make it seem like they’re some critical privacy thing, but these days virtually every website is encrypted (HTTPS). Your ISP can know the IP address you’re visiting (and thus typically the site), but pretty much everything else, including what page you’re viewing on the site, is known only to you and the site in question. VPNs had a lot more merit before HTTPS was ubiquitous.

They’re still useful if you’re visiting illegal sites or using peer to peer technology (most particularly illegal torrents), but that’s not the case for many and certainly not for just viewing normal porn.