I'm not an expert in CPU thermals by any means, but from what I've gathered, in order to eek out a tenth of a gigahertz for their marketing materials (with rapidly diminishing returns because physics), manufacturers usually set Turbo Boost Power Limits 5-10 (or more) watts too high. Since Turbo Boost usually maximizes a single core's frequency and the heat generated increases exponentially, it creates a very concentrated heat spike in the silicon. Even if the CPU heat sink is good enough to passively dissipate that much heat from all of the cores, the turbo boost hot spot forces the fans to spin up early before the CPU knows how long the boost will be needed (otherwise Turbo boost would significantly reduce the lifetime of the CPU). Combined with random scheduled OS tasks that take a split second of turbo to run a process and firmware configured with a minimum fan running time to avoid even more annoying pulsing, these power limits cause many mass market laptops to needlessly spin up their fans all the time.
It's ridiculous but I've been running ThrottleStop/the equivalent on Linux to under-clock every laptop I've owned since Turbo Boost was introduced. A small 10-20% reduction in turbo boost power limits is rarely noticeable unless you have a very specialized and irregular CPU-bound workload but it makes a significant change in the amount of heat it generates and gives the passive dissipation enough time to absorb a boosted workload instead of spinning up the fans in an emergency.
The general advice is to never ever leave the factory configuration in place (if you're not going to install Linux at least reinstall windows)
Hardware manufactures are, in general, not your friends.
What if the "no discernible reason" is just poorly coded software?
Fans spinning up is an indicator of something. Usually an indicator that the machine is under heavy load and you need to watch out for the things that come with machines under heavy load: slower performance, overheating, graphical artifacts, potential crashing, etc.
If my fans spun up when I was not aware my computer was under heavy load, I would believe something was wrong with my computer. If I spent any amount of time researching why my computer was under heavy load and my conclusion was that it was not under heavy load and that the fans just spun up for no reason, I think I'd be rightfully irritated.
Imagine a doorbell that rings randomly even if no one is at the door. In the grand scheme of things it's minor. But it shouldn't be happening, and every time it does I have to get up and walk to the window to see if someone is actually there. Every time the doorbell rings and no one is there, I'm going to get more and more irritated.