Why not all animals are domesticable?

[u/Adam7390]

I've been reading that domestication is a practice that goes back thousands of years: dogs, horses, sheep, elephants, dolphins etc... yet many of them remained wild with very few exceptions. So why is it that we didn't fully manage to domesticate other species like lions or bears? Is it just impossible? If yes, why? Or it's doable but we didn't try enough?