It's not surprising - Twitter is a dot-com bubble company a decade after it happened.
That was the ORIGINAL problem with many internet companies. They could find out how to draw in lots of users and get popular - they just couldn't find a way to actually make any money from it.
Depending on the site, SOME companies can make enough off ad revenue to be successful, but Twitter has never managed to do so. And I'm not sure it will work there. With their format of limited post length and being largely a spew of conciousness they've to some degree attracted a userbase that has a short attention span. It's hard to effectively put ads in front of them.
There are plenty of internet based companies that have figured out how to thrive - Amazon, Ebay, Netflix, Google, etc - but I'm not sure Twitter will last. If it goes away I don't think there will be too much of a problem though. Social media as a phenomenon will likely continue just fine. Facebook (who also runs Instagram) is operating in the black.