[akvadrako]

Take home tests are often paid and those are the only ones I will do anymore after being burned a few times.

That solves the skin in the game problem.

[avnigo]

If they're not paid and you still wanna do it, make it into an interesting problem you wanna work on and have it be presentable enough to include in your portfolio.

At least, that way you might get something out of it instead of nothing, although I definitely do agree that being paid for it is the only way to solve the skin in the game problem.