It's hardly the various sites fault.
Wonder what would happen if the morons/non techies (delete as applicable) can't use whichever password they have chosen for EVERYTHING on a site they will persevere? No, they will go else where.
If this happened to, for example, my mum she'd go elsewhere.
"I tried to sign up but just got errors/some message I didn't read in red letters so I signed up to $Competitor instead and they let me use "password1" just like facebook, my bank, amazon and tesco did"
If I was a techie working for (agian for EG) tesco and I pointed out that we suspect fully 33% of our userbase uses "password" or VERY close equivalent for their online account what do you think my boss would recommend? Force the issue upon next logon? Spend months emailing people advising them to change their password? A pop-up saying passwords must now meet X,y or Z standard?
They'd all be ignored. Totally. Try and force my mother to do this and they may as well send her a link advising her to shop online with Sainsbury instead, because that's what she'd do if she tried to sign up or log in and it wouldn't accept her "one password to rule them all" which is, incidentally, "password" and, in extreme circumstances, under much duress from her works IT dept "passw0rd1"