That's a little myopic; it's just another business model. They could instead price an app itself at $99 or whatever is desired to support development, marketing, profit, etc costs, and not have any in-app purchases.
If anything, game companies are doing exactly the opposite by charging full price for a game (mostly ~$60) and filling them up with in-game purchases anyway. Loot boxes, skins and other cosmetics, battle passes, etc.
