Speaking as someone who on a variety of occasions has been asked to bake these kinds of restriction into a piece of code, I've tended to follow the restriction to the letter but not the spirit -- yes, this product has "DRM", but yes, any child with a hex editor can disable it in a few minutes.
From this I guess that weak DRM is very often entirely intentional.
As for the kind of engineer that does it, you do. Or more accurately, every engineer who has ever been asked to place their ideals ahead of their paycheck -- and realized jumping ship simply wasn't worth it