Note for the downvoters who might confused: I’m using multithreading in hardware sense of symmetric multithreading (SMT), which Intel refers to as HyperThreading:
Hyper threading is indeed meant for languages like Python or Javascript that use pointers everywhere. Once you have an optimized workload with little pointer chasing the only other meaningful benefit of SMT come from the fact that you can run floating point workloads alongside integer workloads. That's a pretty rare situation but it does happen sometimes.
That was basically my thought: there are plenty of programs which it can help (almost all business apps) but not all of those are limiting anyone’s work and the feature isn’t free. Having multiple true cores has been common for multiple decades now and I’d be really curious whether a modern chip design team would feel it’s worth investing in if they didn’t already have it. My understanding is that SMT has a power cost comparable to extra cores and given how well Apple’s CPU team has been executing I’d assume there’s been careful analysis behind not implementing it yet.
https://en.wikipedia.org/wiki/Simultaneous_multithreading