There are a lot of legitimate uses for IAP, for example games that sell additional levels. There are essentially 3 types of IAP: non-consumable, consumable, and subscription. The type you are referring to (consumable) lends itself well to predatory practices, but I dare say 90% is hyperbole. Apple has taken steps to mitigate the issue, and a lot of times it's pretty obvious when the developer is just trying to nickel-and-dime their customers to death.
A lot of developers rely on using IAP to make money off their existing (and often small) customer base, and if IAP went away so would a lot of indie game developers.