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Zenith and JLC also make some lovely slim watches. I have a Zenith El Primero chrono that's only 10mm thick - pretty svelte for a chrono (though it is hand wind).
tertius-
Had no idea they ever made a hand-wound El Primero (given the name refers to it supposedly being "the first" automatic chronograph movement).
Yeah, there are thinner watches on the market for sure. I honestly think that thinness is something that generates a lot of noise in the comments sections but probably doesn't affect overall sales all that much. Same thing as date windows. A vocal minority hates them, but many customers would never buy a watch without a date. Again, same with automatic winding.
Having said that, looking at the market I think there's a shift happening towards more choice. There are more options now for people who want something smaller / hand wound / without a date. The watch internet (by which I mean recent stuff like Hoodwinkee, Instagram, Teddy Baldassarre etc) and online groupthink is definitely changing what people are demanding from watch brands. But it takes a while for the brands to respond to that.
Regal
The chunkiness is in large part due to modern movement design prioritising robustness, shock resistance and serviceability. People expect stuff to “just work” now. Longer power reserves and automatic winding are also a factor.
It’s also a longer term fashion thing. What people expect a watch to look like. At one point 36mm was considered a large mens watch, and now most companies see 40mm as a default average. There was a fad for ultra thin watches but it’s long since faded (though Bulgari are still breaking records) and now the luxury steel sports watch (the Rolex archetype) is probably the most popular design.
There are exceptions - eg Nomos make a number of smaller, slimmer mechanical unisex watches - but I’m sure a lot of blokes would consider them effeminate.