This is an insightful comment. Thanks. I wonder how things would change if a second core was sitting idle anyway, like in a mobile app that does everything on the main thread. Would it then make sense to utilise the second core for greater performance? Imagine memory isn't a problem — some phones have plenty of memory, like 6GB on a OnePlus.
Unrelated to all the above, and related to your point about uncollected cycles not being a problem with refcounting, it does impose an overhead, like remember to use weak pointers to delegates in Objective-C. It's not as seamless to the programmer as GC. You can argue that it is (not) worth it, but there's no question it's more work for the programmer.
Apple's phones tend to have less memory, and fewer (but faster) cores. Along with Objective-C's reference counting, I think those are very smart choices for typical mobile app workloads.
In principle having lots of cores available is great, but in practice it's hard to utilise them effectively without also using tons of memory and/or battery.
Unrelated to all the above, and related to your point about uncollected cycles not being a problem with refcounting, it does impose an overhead, like remember to use weak pointers to delegates in Objective-C. It's not as seamless to the programmer as GC. You can argue that it is (not) worth it, but there's no question it's more work for the programmer.