Does it, though? I feel like most people just use their phone, and that's it, and people who use the web version don't mind so much that they need their phone on the internet, because it pretty much always is anyway.

Sure, there are edge cases, like being on a plane and only having bought internet access for your phone, phone battery dead and no charging cable, phone lost/stolen, but those things seem rare enough that most people just live with it.

I would prefer that I didn't need my phone to use WhatsApp Web, but in practice it hasn't kept me from using WhatsApp (mobile or web).