Developers are good at creating mental models of how the system probably works underneath. Non-developer users usually don't do this. If you're making a product for non-developer users, your subconscious tendency to model the system is a disadvantage, because you won't have a reliable sense for what's intuitive and what's not. If an abstraction leaks, you'll see straight through it and manipulate what's under the abstraction; a non-developer user will continue to try to manipulate the abstraction itself.

This disadvantage potentially extends to managers whose job includes understanding what the abstracted-over system is, but they're probably not thinking about it as hard on a day-to-day basis as the developers.

(Note that "non-developer users" probably also includes developers whose expertise does not extend to the specific system in question and therefore have no ability to guess what's leaking across the abstraction barrier, e.g., Linux users trying to use a Windows tool, new employees figuring out your in-house build system, etc. etc.)

Totally. Most of developers I know are unable to see what people want. They are good at technical point of view, they are good at recognizing patterns and read data, but usually they are unable to connect all the dots and make something beautiful.

I started developing just 3 years ago, after shifting from marketing and sales. Its amazing how most developers lack social skills needed to understand user trends. Yes, product managers are important to connect technical point of view with more abstract one. No, not all developers are like that, but I would say 2/3 at least.

Developers are mostly good at creating products that they would use. Once they enter ground where they create product for others - thats when difficult part begins.

I wonder if any of these 2/3 of developers ever had a service job? Has it gotten to the point to where they're like football players, and all they've done since the sixth grade is code?