You don't need to trust others. For example, build the password using some simple algorithm that uses the TLD name. This way you only need to remember the algorithm.
Second, sometimes sites mandate that you change your password. Or have rules that are incompatible with that algorithm. And then you need to start remembering exceptions to your algorithm, at which point you're back where you started.
I gave up on it for the same reason. Having to remember exceptions, plus when you change your password, you have to change it everywhere, which is annoying because you can't remember every active account.