@Android_Nanaif you see 10 skins for Caustic, you will spend £15 to get only one that looks the best, but if they offered to you in limited time events, you might actually go for buying more than one skin, because each event give you 1 skin and you can not compare it, and it also gives you the idea that this skin will be rare and unique.
In other games, there is nothing rare or unique, everyone can purchase the best skin and all players will look the same at the end; also why would you buy a good skin when you can see better skins are presented at the same time for your specific legend?