Without a lift or something like QuickJack, these are necessary for safely doing simple jobs such as brakes, wheel rotation, etc. on later model Porsches (and other makes) that only have one accessible jack point per corner. (Can't use a typical style jack stand if the floor jack has the car lifted at the exact point where the stand needs to go.

They'd also certainly come in handy for track days if trailering your car and needing to do tire/brake/other service work.
John Walton was great to deal with - he's also a Porsche owner! (He and his product are featured with Jay Leno in this YouTube episode of 'Jay Leno's Garage'.
Pics of mine from today: