Agreed on the 100K thing. It's a hang up from the days of rope piston rings and monthly decokes
No matter what the make and model of car is, one fact always prevails: it's lifespan is directly proportional to it's upkeep.
Have you guys seen the 200K GTI project on youtube? TR Hamza is the channel. Seems in pretty good shape for the mileage.
The reason for the cambelt and cam chain is usually packaging, and to a lesser degree, ease of servicing. If you look at an old Vauxhall redtop 16V engine compared to a MK2 16V engine (less manifolds etc), the VW unit is a lot smaller. And, similarly a more recent Vauxhall engine that uses a pair of cambelt driven VVT adjusters is a taller and broader engine compared to EA113 and EA888 engines.
Car makers fit chains to reduce engine size, and also to entice customers into buying something that's 'maintenance free', but everyone knows by now that's a myth. Thank your lucky stars you don't have an Audi 4.2 V8 or an E39 M5 V8. Try pricing up and doing a chain job on those bad boys!! Engine out on the Audi as the chains are at the bulkhead end