Very true. In the cases you've described, I've power-sawed the underlayment out beyond the cabinet face to remove it. Then, by hand, I'd remove any 'strips'. It does take longer than removing a luan or the like but was doable.
Gail: In most cases where a 1/2" or 5/8" underlayment is laid, you could be 'exposing' hidden problems. 1/2" or 5/8" is used, in many cases, where skim-coating wasn't a 'good first option' (like there was need for 'better support' of the floor, or something). So be careful what you're removing. The key in removing just the vinyl is getting rid of as much as you can where skim coating will 'cover' any imprefections.