One of the other theories I've heard is that it's partly because 4 is an unlucky number in Chinese, which is a major market. Thus why so many SoC vendors pushed to 8 core chips instead of taking those extra transistors and spending them on an L3 cache instead, which would have helped real world performance far more than the extra 4 cores do.
Probably not very true, but it's a fun theory. More likely is it just looks better on the spec sheet to have more cores & ever higher burst-only frequencies rather than the things that would have more bang/buck on more real world workloads like an L3 cache would. It's why you ended up with ridiculous nonsense like the Helio X20 & X30 (10-core SoCs with only 2 good cores and 8 low power ones)
Those low power cores don't take up a vast amount of die area, but they substantially improve battery life. Apple seems wedded to the idea that 12 hours of screen-on time is sufficient, so they're happy to keep pushing for maximum performance; other manufacturers are willing to trade off a bit of performance for a lot more battery life.
2 low power cores help battery life as they can handle all the screen off and background activity. 8 low power cores is just stupid. That 10 core chip in practice will function like a 2+2 quad. The other 6 low powers will be doing nothing of value at all.
Probably not very true, but it's a fun theory. More likely is it just looks better on the spec sheet to have more cores & ever higher burst-only frequencies rather than the things that would have more bang/buck on more real world workloads like an L3 cache would. It's why you ended up with ridiculous nonsense like the Helio X20 & X30 (10-core SoCs with only 2 good cores and 8 low power ones)