Say you could learn to build aircraft engines, understand how the economy works (which has a huge influence on people's lives) or learn how to make a computer print "hello world" on a terminal screen and how to efficiently store data. Most people wouldn't choose the latter. It's actually quite hard to describe what computer science is and why it is a science.
Or the other end of the spectrum, where you are a cube-dweller, who shuffles endlessly to Scrum meetings, does email, enter garbage into JIRA, and once in a blue moon gets to write a little code that might possibly be executed as part of some faceless, soulless enterprise monstrosity.
Also, in the end, big companies like Google and Facebook are IT companies, or advertisement companies, and they are after your private data. I guess most people would rather choose a more noble goal in life.
And finally, tools created by big companies such as Google docs perform worse than wordprocessors of the 90s. Yes, they allow collaboration now, but still, they are perceived as slow. In people's minds, IT is not progressing much.