> I will never undertand this people that live all their life working, when they clearly have the chance to retire much sooner.

Some people just love what they do. In addition to people loving what they do, there are also people who don't like to do nothing: travelling, reading, sipping pina coladas in the pool in Florida, painting, playing videogames all day long etc. is not for everyone.

And there are even people who fit both: they love what they do and they have moreover absolutely no interest in retiring and "doing nothing".

EDIT: also some people are action junkies that must be working. A friend of mine is working a full-time regular job and is also a voluntary firefighter, responding to emergencies during week-ends etc. He doesn't do it for the little additional money it brings: he does it because he loves to be helpful.