I think it would be like suggesting people give their life savings to their unreliable neighbor to hold on to. It might be safe, and might be secure, but at the end of the day they are being asked to bet everything on something they don’t find to be reliable.
In the end, perception is reality and I can’t say I entirely disagree with the perception. I use a password manager, but unless you are running the infrastructure and backups yourself, which a normal person isn’t going to do, you are at the mercy of “corporations” that we know to make mistakes, have data breaches, lose data, change their policies on a whim, break the law, and even cause people’s deaths, all while suffering few if any consequences.
I’d say the average person’s hesitancy toward using a password manager is probably pretty justified, even if it would be far more secure.