When browsing for apps there you may see a top app being free and another costing $1. You pick the "free" one and it turns out it is useless without an IAP whereas the $1 app perhaps would not. It turns out the free app costs $2 in order to function as well as the $1 app.
The consumer friendly thing to do would be to list any app that has any IAP enabled to be listed as non free, either using some special labeling (category "freemium" rather than "free"), or by listing the price as an interval rather than as the minimum.
It's come to the point where I really miss the time when many apps existed in two separate versions, a free and a premium version. Would that not have been the solution to this problem?