I guess I am old fashioned I was never convinced extended service intervals and belt changes were either the spawn of manufacturers marketing department to gain an edge in the fleet markets, or engines had genuinely improved. A bit of both probably.
Early 90s the market significantly changed, due to recession a lot of fleet buyers stalled changing typically moving from a 3 yr 60 k to 4 year 80 k cycles ...which is the norm today , what they found the costs incurred for the additional year was minimal so the overall whole life cost of ownership changed and they latched on
For a modern garage shortened service tines, extended intervals makes filling the ramps a challenge for service managers the less scrupulous invent work ( sure no one believes that)
Peace of mind is a motivating factor with vehicles and prevention better than cure cheaper too ..to my mind changing belts, oils and fluids makes a lot of sense
I mention the fleet markets because that is where the lions share of production finds itself and is marketed at
Channa