I'm going to take extreme issue with your use of the word "often" here.

Anyone technically minded used FTP back in the days. So why is there a need for Dropbox (at that time).

That is what makes it hard to invest if you think too much or "know" too much. You get blinkers that prevent you seeing what become obvious successes because of UX improvements for the non-technical crowd.

Knowing the subject well may put blinders in some situations… but what’s the alternative? Know the subject poorly, flail about wildly and hope you land something by pure chance? Obviously knowledge isn’t the problem here; you need it to qualify if it’s a good decision or not. It’s the over-specialization, combined with the lack of empathy for the average user that derived the dropbox event.