It's not about solving important 'problems' for most - it's about how they can make the most money, and that is usually by providing more convenience to people.
This is, of course, how business works in a capitalist society - the issue is that the problems they solve are often marketed as being the most important, whereas they're just selling a dream.
I'm sure they would solve the major problems if they could and there was sufficient money in it - look at how the drugs companies operate - but this is (and has always been) about money.
Amazon are running their competition for better robot picking - are they also running competitions for how to help people whose jobs are replaced by robots ?
Silicon Valley has a single role - to make (more) money for those people investing into it. That's all. There's little to no philanthropy, and when there is it's generally from people who are already far wealthier than is required to live (an excessively comfortable) life.