IMO major reason for the aversion to changing timing belts on a regular basis, is in many instances down to very poor accessibility and complexity, which obviously greatly increases time and labour costs.
One could therefore be excused for thinking that as it's an essential service item which should be replaced on a regular basis, the manufacturers would put a little extra effort into making the job of replacement relatively simple, i.e. a classic example being the much-quoted clutch replacement on the Mk2 Vauxhall Astra.
The timing belt (along with the associated water pump) on my old petrol Astra was a relatively straightforward job to do, especially after having been done once.
Whilst the GM diesel version I owned required the removal of an engine mount, rocker cover, and the use of a DTI tool/slide plate for timing belt replacement, IIRC all the alternative Isuzu engine required was the use of three locking studs for alignment.
Call me an old cynic Conor, but I'd go as far as to say that motor manufacturers have a vested interest in thousands of cars prematurely winding up in scrapyards!