[BeetleB]

If you look at most advice given on using spaced repetition well, the standard advice is "Don't learn random stuff" and usually some other advice on ensuring what you put in your cards is meaningful to you.

For me, there is a bit of effort required in creating the card. That alone makes me only put in things I think are meaningful to me. Lots of times I learn something interesting and think to myself "I should make a card out of that", but it's too inconvenient. As such, most of my cards are for things I am intentionally studying.