Why isn't Gladstone Gander richer than Uncle Scrooge?

Gladstone doesn't care about being rich. He relies almost solely on his luck to get him what he needs or wants at the moment. Who cares about being rich if you've got everything you want (that money could buy)? Well, OK, Scrooge would, for one - but it's pretty clear from his attitude that Gladstone doesn't.

In fact, I vaguely recall a story (in the comics - no, I don't have the reference handy on that one) that showed that Gladstone's luck wasn't reliable if he tried too hard - that it only worked as long as he kept his laissez-faire attitude.

This story might be “Trail of the Unicorn”; here, Gladstone tries to cheat Donald out of some money. Gladstone theorizes that cheating is a form of work, and that’s why his scheme fails. (Thanks to McTroopers for the tip).