What if you build something you want for other people, but they don’t want it? You might be satisfied that you have built something but disappointed because nobody else wanted it.
What if you build something you’re not too thrilled about but people love it? You may feel unfulfilled or bad. They are satisfied and buy it. Crucially though, it allows you to build something for them again, and maybe this time, they’ll have open minds because of your previous work.