Naive question: aren't belts lower maintenance than chains, and don't let last longer? Why doesn't a engine with a chain drive require equal or more replacements?
On all of our other cars (Toyota), the belts needed to be serviced at X miles, but it was actually a cheap and quick procedure.
After 2017 Ford started using belts to drive the oil pump in F-150 engines (and possibly other Ecoboost engines). I have seen 100k teardowns of failed engines and the belt is not looking good at that point. If the belt breaks the engine is toast by the time the operator realizes what is going on.
A caveat though. I used to have a Škoda Fabia with a chain drive, and I did end up changing it, as it started making the tell-tale sound when stop-go.
In the context of hybrids though, I fully expect that chain to last the lifetime of the engine. The engine is under significantly less load than in a traditional ICE, so less stress on the chain. Also, for 100k mileage, the motor-hours that the engine has worked are less than in an ICE due to the engine regularly being off.
My Land Cruiser has a timing belt. I replace it every 90k miles per Toyota's specifications. My Tundra has the same engine, except that it has a timing chain. I've never bothered to replace the timing chain.
A timing chain is preferable as long as it isn't something like a Jaguar/Land Rover. The chain in those doesn't matter because they use plastic tensioners that eventually become brittle at crack/fail.
Chains were very common in American cars and trucks for decades and they did need replaced after 150k-200k miles. I replaced the one in my 1993 Ford 5.0 at about 150k hard miles and it made a dramatic difference in performance (solved knocking/preignition on hills).