All skins that appear in Lootboxes should be buyable with coins, not sure why i cant just outright buy most of them when they appear in lootboxes permanently

Like, I was just about to buy Cardboard Dva with my coins from UBP bundle and noticed its “sometimes available in shop”, then noticed she is available in lootboxes regardless.

if Blizzard wants $$$ for skins, why are most of them unavailable to outright buy while completely relying on low chance of lootboxes having the skin? We technically could do this in OW1. I dont see why losing the opportunity to make money here? Is it a bug?