Honestly, after seeing what Apple was able to do with the M1, I think it's clear the top answer is performance per watt and high performance. If Qualcomm (or Intel or AMD) could deliver that same level of performance in an ARM SoC, slow emulation wouldn't be a problem. All the Arm-based notebooks I've seen are low-power and low-performance mobile parts that simply aren't fit for purpose.
There is no wide range of software available for 'Windows On ARM'.<p>Windows as a raw base install is pretty useless. Without the huge range of ready-made downloadable software it would be no good at all.<p>The problem of course is that all that huge range of downloadable Windows software won't run on an ARM machine.