Personally I've noticed skateboarding attracts a lot of people with depression. Goes hand in hand with the whole broken family and getting away from them with skateboarding stereotype, which I can definitely relate to. I've got pretty bad depression and I'm not speaking for everyone but it certainly doesn't help me when I'm having a shitty day/week skating. I've been riding a skateboard for 16+ years and I'm nowhere near as good as any of my friends, some of which have been riding for a quarter of the amount of time as me. There's tricks like the heelflip that I can rarely land, yet I have a very good understanding of foot placement and everything else about the trick from watching so many different people do them. The funny part is that I can switch and nollie heelflip a thousand times before I land a single heelflip. When I was younger I slipped out getting into a feeble on a double bar flat rail and got a concussion, that bail really messed with my balance in general because I was able to do them before that but ever since I haven't been able to get over the mental barrier. But I can crooked grind a flat bar and even pop a nollie out somehow. So you can see why I might be a little more prone to more depression, when the one thing I love more than anything in this world is the one thing I try to do to escape everything else and I'm obviously not having a good time sometimes. Also doesn't help that I'm getting older and my body isn't happy with impact anymore because I never pushed myself past a 6 stair. I bailed on a nollie flip attempt on flat 3 weeks ago and I'm still feeling it because I landed on a bone on the side of my foot with all my weight and stepped on it wrong at work today which ended up making me have to leave early. So I'm losing out on money because I love riding a stupid piece of wood. Dumb bails like that are a normal occurrence for me and so many people as well. I don't know about you but it's pretty depressing knowing you can't go and skate because your foot is in pain because you were skateboarding and landed something a little weird because of probability... Now imagine having to give up another hobby completely, like guitar, because you ate shit and put your dominant hand out to catch yourself instinctively and now your wrist is broken in some weird way that will never fully heal plus always hurts and if you keep skating with one small bail on it, you're more fucked. It's depressing, isn't it? Having to basically give up more than one thing you love. Luckily the last situation hasn't happened to me, but I needed a good example and I know people who have the same reasoning as to why they quit.
There's also the factor of how many people grow up with good groups of friends who skate, but over time those friendships slowly fade away because the group slowly quits until there's the one or two guys left who have opposite schedules and can't find time to skate like they used to. That has definitely happened to a large amount of people I grew up skating with at my local, and another of the many things that doesn't help with my depression either because it was a time before social media started getting really big so I've lost contact with 90% of the people who still do skate occasionally but are only ever at the park when I'm not there so I haven't seen them in 10+ years and don't feel comfortable adding them on Facebook because they might only recognise me in person. Only recently started skating again with the kid who happened to be at the park with me the day I slipped out on my earlier mentioned feeble because he moved away a year after that and only recently moved back. My roommate used to skate with me every day and it's the whole reason we became friends in the first place. Now he's had the same board for 2+ years and can't skate because of he has a labour intensive job that he's afraid of losing if he bails. He's more depressed as well than I've ever seen him lately but if I manage to get him out on his board, the moment he lands a kickflip you can see he wants to skate like he used to so bad but knows he can't because he fucked his wrists one too many times when he was younger. So basically the same situation as my last paragraph's example but with just work holding him back. People piggyback off each other's depression because of situations like that, and it definitely happens between the two of us.
But I still love skateboarding and will be doing it until the day I die, or I literally can't even ride one. That's just my two cents.
tl;dr - tricks hard, bails suck, me old baby with barely any friends left who skate and almost all the ones who do also are depressed. small bails risk losing job and having to give up other hobbies. still love skateboard.