Why do they say Retired when you never really worked

[Danzig]

----and for American breeders, as much as they might want to race their male horses longer, they are often forced to sell or syndicate because the Internal Revenue Service (IRS) has a rule that you have to make money two years out of every seven or else you could be declared a hobby and not a viable business that is entitled to write off expenses. You don't want that.

the above is from an article about early retirement of racehorses.