I know for a fact that some mobile gaming companies model how often players need to win to ensure that they stay engaged, and de-randomize to (as best they can) ensure players win "often enough". That said, the reason I know this is because I know of the technology, and I don't know how widely it used.

Personally, I wouldn't buy a crate any more than @DarcyMardin would. But I've played ESO since beta, including during the periods when free crates were more common than they are now, and have gotten about 600 gems total. 400 were spent on exactly the mount I like best; 40 were spent on an Arctic Rime skin that I now regret due to the vampire changes; and the other 175 or so are currently banked.