I want to say I agree, but I don't know anything about how businesses work so I might be missing something. Someone must think there must be something of value there, otherwise they wouldn't be investing in those companies, right?
Yes. But what they consider valuable isn't always what (say) a small business owner would consider valuable. Small business owner is looking at profits, overhead, taxes, etc. Investors are more interested in whether users like the product/service, whether they stay around, etc. The idea being, that if people love the service, eventually you can find a way to monetize it. Facebook, for example, didn't make a profit until 2009 (I could be wrong), which is two years after they soaked up the migrants from Myspace, and five years after the company launched. Five years with no profit is absolutely insane if your business is selling burritos.