The way I see it, password reuse is a matter of cognitive load. Most people are unable or unwilling to attempt to remember the umpteen dozen unique passwords they would need on a daily basis, if they where to attempt to use unique secure passwords on every service/device they use. This results in password reuse, more or less out of sheer laziness. It is probable that among this group, there is a cognitive bias against using password keychain services and tools, because it 'feels' like putting all your eggs in one basket. (somewhat flawed) Logic dictates that if someone breaches the master password to your keychain, and they have all of them, which is no different than using the same password everywhere. (of course, this is not entirely the case, but like I said, cognitive bias)
Now, as for using 'good' passwords, it follows a similar pattern, with most people unwilling to dedicate the time and effort to memorize what amounts to a 'good' password, when they can remember their spouses birthday and their first pet's name just fine.
Of course, we have seen time and time again articles arguing both sides of the court, that long random passwords are either effective or not, and correct horse battery staple passwords are effective or not, so this portion of the discussion is going to be long, stupid and frustrating for evangelists on both sides.
Honestly, I've reached a point where I use 'good' passwords where it matters, (main email, financial items, Amazon etc) and just sort of hope for the best when I re-use the same 'decent' password everywhere else (forums, etc)
I say 'good' because we're at a point there have been enough breaches that we're all probably fucked anyways.