'JR' I'd say that there are somewhat shifty people both sides of the fence there, A/C owners & spanner-men. Both have an agenda, right or wrong it's human nature for some to think unwise at times.
As for TBO's, well they are a bit like SWL's on cranes for EG. The crane could handle usually twice the SWL as placarded on the Jib but for a whole variety of reasons mainly to keep it as safe as possible it's halved or thereabouts because of unknown handling of same during it's nominated lifetime. Same goes for an A/C engine in many ways as you can't rely on an A/C owner to treat, respect & service an A/C's engine exactly to the manufacturers specs during it's whole life mainly 'cause of cost, the varied environment these engines can & do run in & the amount of different operators over the say 2000 hrs of it's 'expected' life.
Continuing on past an engines TBO on condition is testament to the fact that they 'may' run longer given a certain set of parameters met but that same 'acceptance' or belief isn't extended to commercial Ops, now I wonder why that is? Obviously that comes back to public safety & risk, the "SWL" factor:-).
A line in the engines 'sand' regrading hrs it could run has to be drawn somewhere for the good of all & the manufacturers are also covering their ass here as in 2day's crazy litigious world who'd in their right minds would wanna produce anything other than say cotton wool!
Wmk2