Why is automatic detection of corners so bad?

Adobe Scan has a great feature that is detecting the four corners of the sheet to straighten the image. Or it would be great if it worked correctly.

I have tried it with a completely flat sheet with no bent corners or warping on a dark table and even so, the markers are never exactly in the corners and I have to adjust them by hand. In most documents the aproximation is good enough but some others need zero distortion and even if I try to place the camera as exactly right above the center of the sheet as I can so distortion of the capture is minimal, the software doesn't do its work correctly and I have to readjust the corners by hand.

In the days of emerging AI it seems weird that a software by Adobe doesn't seem to do such a simple task (at least simple when the user provides all means to facilitate the task) with more precision.

Also, there should be some way of detecting curved paper (typically the pages of a moderately thick open book) and warping the image to straighten this distortion.