People often use insecure passwords or use secure passwords but struggle to remember them. Password managers seem to provide a nigh perfect solution to this, allowing users to create very secure passwords while preventing them from needing to remember all but one of them. Despite this, many people do not use password managers, not even ones built into web browsers like Chrome's. Why is this? If it is because people do not know about password managers, why don't they? Why aren't they mentioned in school, for example?
This is going to be a rather subjective question, so don't expect it to be live for long time..
In my case, I don't see any benefit on using a password manager. In fact, I consider passwords managers are a bigger threat than "weak" passwords, for the reason you already mentioned: one password to own them all.
That question has a lot of sub-questions, but I try to answer them as good as I can.
There are two factors why most people don't use special password manager programs like KeePass.
- They don't know about password managers and potential benefits
- They have heard about them, but don't really care
Using extra software for managing your password may seem reasonable for somebody working in an IT-related field. For most people it is additional hassle. They need to choose a product and learn to use the software. This requires time and effort.
This also answers why people don't use password managers shipped with browsers. If they don't know about that feature and it is disable by default, then how should they use it? In case were it is enabled by default I would think that the statement is false and it would be used very often (this depends on the browser though).
I would even go further and say even many people working in IT don't use password managers either because of 2. or because of technical reasons. Password managers are a potential single point of failure, especially when using online password managers. For proper security you do have to take a closer look at the products and features.
The third point would be, that there are other solutions to the problem. You could simply write the password down. That is pretty much what most people do.
Why password managers are not a topic in school is pretty much obvious. If the teachers don't know about it, how should they teach? Not every school as IT-classes, even those that do likely won't cover such topic.