Imagine you get approval to build a new park and playground for your neighbourhood. You spend hundreds of hours designing the plan and layout and you spend incredible amounts of your own money to get the resources.

You get to work and things are going well. As you near the end of months upon months of work, the park finally opens for families and kids to use.

As you're standing there proud of your work, some people come over to you. Do they say "thank you!" or "you did amazing work"? No, they come over to complain about things that are missing, tell you what you should have done better, that you didn't accommodate their each specific needs, etc.

You would very quickly get bitter and demoralized.

Like I mentioned before: this is a massive problem in the open source development world and has killed many great projects. This has nothing to do with "mental attention" and everything to do with users abusing the devs and their time.