This 2015 MacBook Pro will avoid turning the fan on at any cost. I frequently watch the CPU package heat up to about 190F while the fan is still at 0RPM.
Further, the SMC chip and/or kernel are set to use fairly slow fan speeds compared to the amount of heat being produced, so even when it does come on, the system remains hotter than necessary.
But, here's the major problem: it's also become clear that there is a thermal window where the system is hot enough to cause it to throttle itself, perhaps somewhere between 140F and 180F, but not hot enough for the SMC to turn the fan on fast enough or at all, even though it could and should.
So in addition to being really hot and not using the fan to get the heat away from your lap, it gets slow at the same time, right when it's being used. The system becomes faster soon after the fan is turned up to the max.
And to top it off, there appear to be two different throttling mechanisms, the CPU speed can adjust up or down (you can see this with the Intel Power Gadget), and Apple has some kernel system that will use CPU cycles for idling instead of scheduling threads that are waiting, which reduces overall CPU usage, and therefore also heat production.
All combined, it looks like the system is constantly bouncing between ramping up the CPU frequency to handle load, then wasting some of the additional CPU time idling to avoid turning the fan on, then turning the fan on just long enough to get the heat down before turning the fan back off again, and repeat.