Photoshop 2019 refuses to place images when the resolution is low

Sometimes we receive images with enough pixels (6000x4000 e.g), but with the resolution set to 1 px/inch, for some reason. These images won't be placed by Photoshop, without mentioning why it refuses to do so. Setting the resolution mannually, to 72 px/inch or higher (without resampling) and Saving, resolves the problem. The newly saved images can be placed.

But the question remains: why doen Photoshop give up in the first place?