Resilience, endurance, learning to overcome adversity, learning to overcome yourself, learning to be self-aware, thinking "differently". I could think of dozens of other reasons. No?
I'm not sure these are good examples, but depressive realism is a pretty legit hypothesis about a potential evolutionary benefit. There's also some hypotheses about energy expenditure - doing nothing is sometimes the right move, although that would have been more important a long time ago than now.
These sort of ideas are hard to evaluate definitively, but I do think it is plausible that mild depression had/to some extent may still have benefits. Of course certain traits can be taken too far though, and when viewed through that lens it is hard to understand how they could be beneficial at all. One could say a similar thing about Autism-like traits.
Depression affects everyone differently. But it does not mean a constant unending, it can come and go and those peaks and valleys lead to what I'm talking about.
These sort of ideas are hard to evaluate definitively, but I do think it is plausible that mild depression had/to some extent may still have benefits. Of course certain traits can be taken too far though, and when viewed through that lens it is hard to understand how they could be beneficial at all. One could say a similar thing about Autism-like traits.