Bullshit. Tech companies are not competing for worldwide talents. The companies you quote have at most 3 offices in Europe: London, Zurich, Dublin. The first thing a recruiter will tell you is to abandon your life and your family.
Do you mean that as in "move" or as in "work long hours"?
Google has at least offices in Germany, too.
Google has offices in almost every countries but they are administrative offices with almost no employees. If you're a tech worker, you can only be in one of the very few tech locations.
But you are right, that those are not big major tech offices like the three mentioned. So most engineers in Europe would still be working out of London, Zurich or Dublin.
Relocating means leaving uncles aunts, cousins, mom, dad, grandma, etc. And any friends you have.
I've had to explain to many recruiters that leaving all my friends and family and my community as a whole is just not an option.
Changing country is changing everything.