Because they're unique items that don't reuse assets. For example, you could choose to apply your mod to mogstation item #123, or say, a Hempen Doublet, which shares its model with many other doublets.
The only time the money spent in a game sees a % of the profit going back to it is if the company in charge focuses only on that product.
Almost no video game company operates like that. Everything goes to the company and shareholders' pockets. Budget is decided on a per project basis no matter what.
Ngl, if something like that exists in this game, I'd do that. I'll grind for 2 hours for something like an emote. I won't fork out the money, but at least I get something to work on for in this.... content starved periods, especially. The grind is also optional, so anybody who don't wish to 'waste' 2 hours they can pick up their wallet. Sounds like win-win situation to me.
Buying items from the mog station seems pointless.
There isn't a mount, emote, hairstyle, glam I don't get board off.