Problem is no that developers doesnt know this, problem is when the company says "we need the passwords in clear text because customer are asking for them", and you try to convince them it can be reset and they say "but email is reliable, we need to be to give them the password"...and so on. Also, the idea that centralizing would increase security is deeply flawed, eventually someone will hack one of these solutions and then tens of millions will be compromised rather than one website.