Excellent advice, you can never hear stuff like this enough times. I don't buy everything I want/need. There is some stuff I simply care more about, and that's where my attention goes.
In addition to asking 'does the customer need this?', you should ask 'does the customer KNOW they need this?'. If the answer is no, your startup has two insanely difficult problems instead of one.
Your second point illustrates the difference between a latent need and an active need. It's difficult enough to gain attention for active needs, yet alone latent needs.
I used to think the same way. The turning point for me was reading Jordan Mechner's development log for the original Prince of Persia. It's long, but worth it:
Basically, after the game was finished they spent two years expecting a word-of-mouth breakthrough which never came, then tried traditional marketing and had a huge success.
In addition to asking 'does the customer need this?', you should ask 'does the customer KNOW they need this?'. If the answer is no, your startup has two insanely difficult problems instead of one.