Placing new pad on top of old?

Contractor said he will place the new outdoor pad on top of the old one, after re-leveling the old one.

My question: Is this common practice, or may he have an ulterior motive such as cost & effort of disposal?

Thanks,
Max

source https://hvac-talk.com/vbb/threads/2227444-Placing-new-pad-on-top-of-old?goto=newpost