Sometimes you spend some money on the game simply because you really like it and want to support the developers.
I occasionally buy skins for fighting game characters simply because I enjoy looking at those skins (more than I enjoy the defaults). Heck, some characters are played exclusively because of cool skins (e.g., Blanka Chan).
I see no problem spending money in something that just looks cool if you're getting your entertainment value from the game. It's the same reason why you would buy that cool shirt you saw on the internet: you already have plenty of shirts, you don't actually need one more, but it would be cool anyway.
I realize you can buy skins directly on the steam market, and avoid the whole random factor, but then you're just paying whatever the market rate is for "coolness" plus the costs of all the other people who did the key/box buying. Plus there is the whole "condition" mechanic, so the skin you get might not even look the way you actually want.
Like I said, people can do whatever they want, but to me its just silly. When you add to that the fact that Valve actively* stops people from playing on custom (i.e. private) servers with modded skins available and it just seems like shitty anti-consumer behavior.
Boxes are obtained for free by simply playing the game. You don't really need to buy boxes unless you want some specific one from a past event that is not available through the game anymore, but someone got it back then or if you want boxes at a faster rate than the regular gameplay provides. But you need to buy a key to open it, however.
Also, a given kind of a box contains one of the finite number of items. I think the idea is that if you get a duplicate that you don't want, you can either trade it with a player who doesn't have it for a skin that you want or sell it on the steam marketplace (so you can use that money on a skin that you actually want).
But I don't really get your hangup on this. If you're going to take that stance, it's almost like what's the appeal of anything aesthetic? Some people like it. Do you think it's ridiculous when someone buys the metallic paint option for a car? Or goes with a different graphic on a skateboard? Or chooses a camo pattern jacket instead of a gray one?
In hindsight, this money could've been better spent, but I won't blame my teenage self for enjoying a little bit of financial freedom.
Of course, you also get those really rich kids that only want to brag, others that buy in order to resell and profit from it, etc.
The same kind of person who thinks it’s impressive that you swiped you credit card a few more times than they did for the same society? Rolexes, branded suits, designer dresses, branded smells, it’s all the same. Products that are effectively the same as cheaper alternatives except the are more expensive and carry along with them the awe of someone taking on that higher expense. That is to say, everyone, including you. You just aren’t conscious about it in the contexts where it happens.
Also, “Timmy can’t join our clan, he’s a cheap-ass who can’t even afford the flaming bucket helmet we all wear.” Is a powerful sales pitch.
I get the mindset, that's how I felt before in every other game, but I'd consider my $50 of skins money well spent even if no one else could see them.
Some people buy expensive watches, cars, clothes etc only to be able to impress other people who care about that sort of thing.
When your circle of friends exist in a game, and they care about that sort of things, you buy this stuff to show off since there's no one around to notice your Rolex.
At least that is why I buy the occasional skin that looks nice to me.