First reason in my mind was that running on Hobbs tend to let people hurry to take off with less warm up, but can this effect be such big?
I have seen this very attitude time & time again. And yes there is a tendency to skimp on checks to stop that next tick of the clock.
It is also a very unfair way of charging customers IMHO. as hobbs times are rarely ever the same as the required pilots logging time ie Brakes off-Brakes on.
Usually people are overcharged. and by the same token if logging your airframe/engine hours using it you are probably doing more maintenance than needed over the life of an engine.
I have seen people being stuck at the hold because of some officias **** of a FISO wouldn't give the "Clearance" for TO and you can end up just sitting on the ground clocking up unnecessary hours, because engine logs as are usually (Except Rotax?) TO/Touchdown