Drupal is made, designed and maintained by more than 30.000 devoted professional developers and tested by a community of over a million active users (web developers mainly) so that you can enjoy a cutting edge technology for free.
For some, this last paragraph might have sounded nice, but i can guess other people can be a bit puzzled by the fact that so many people work so hard... for free!?? Yes, Drupal making is a huge selfless/selfish act.
It's selfless because all of us (drupal community) want to help each other in exchange of no salary, no payroll, nothing. Full stop.
...and It's selfish because we know we help each other in order to achieve the best web technology out there... we want to be number one.
But don't get confused, we don't do it for the fame or the money, we do it because we love Drupal, because we are passionate about our state-of-the-art CMS, because there is a small part of each one of us in it.
The Very Little Agency loves Drupal.
Read more at the Wikipedia.