Any site that allows non-interactive account creation does this. Typically, it'll send you a one-time password out of band (like via email or SMS), you'll log in, and then you'll immediately need to set up a password.
Better-designed devices do this with their default passwords rather than something you can look up in a manual and therefore must be the same for each unit. The password is written on a sticker, typically alongside the serial number.
Firefox has a password manager that I think is enabled by default and will offer to generate passwords for you whenever it detects you're creating a password. The codes it generates look good to me.
Despite browsers' built-in password managers and syncing options, not enough people use password managers (built-in or otherwise). Those few users with password managers who are following best practices are already randomly generating their passwords, so they're not a part of the consideration here.
For users that need memorable passwords because they don't generate and manage their passwords, you reach an impasse: memorability is inversely proportional to entropy. If a site forces its own password generator on users, it will be overrun with password reset requests.
A better solution would be to ask whether a password is absolutely necessary or if you can use another authentication technique. I think we're headed to this model for most items. Rather than requiring a password and either an authenticator app or security token, why not use just the authenticator app or security token?
Solely using an authenticator or token should provide sufficient security ~90% of the time (the other ~10% includes email and finance). Given current password insecurities, many users are already effectively at this level in most 2FA systems.