[king_jester]

Apps that are provided with for free on Google Play, IAP or no IAP, don't have any fear of piracy from being installed from another source. If Google Play is not available when your app runs, if the user could use that app for some purpose, it is a really good idea to make sure it doesn't crash. Indeed, most free apps with IAPs don't require you to buy the IAP immediately at launch, you can use the app to some degree.

[personZ]

don't have any fear of piracy from being installed from another source

Even if they're currently fully unmonetized, many such apps exist on the Play store because they can be updated at any time to include in app purchases, etc.

[DominikR]

It just depends on how much extra cost is invoked by having more users who never pay. (for example support, server costs)

I just don't think that you can follow some rule dogmatically, because for some it might be worth the exposure, for some the extra costs might outweigh the benefits.

This is something that I would decide on a case by case basis.

[npsimons]

I just don't think that you can follow some rule dogmatically

Sure you can, if the rule is "don't write shitty software that crashes". In which scenario do you think users are more likely to buy: when an app crashes with no indication of what caused it, or if an app pops up a message along the lines of "we couldn't connect to Google Play; is it disabled for some reason?"

[DominikR]

I stated clearly, that every developer should aspire to develop apps, that do not crash.