It's a "how many different versions of the same product can we afford to design, tool for and hold stock of". It's not a powermeter issue per se, it's an issue of how many BB standards and chainring standards already exist.
For spider or axle based PMs sold as complete cranks if you produced compatibility for every possible combination of bolt spacing and axle size you could be looking at 15+ products for what is fundamentally one type of powermeter. That gets very complicated and very expensive very quickly.
And as far as Quarq goes specifically, they're certainly not going to make a hollowtech 24mm spindle. Sram/quarq make GXP BBs. When they sell you a powermeter or chainset they want you to buy their BBs for it now and in future. They don't want you to go off and buy BBs from Shimano instead
Hi, thanks. So taking example of Quarq, they make a Shimano version DFour but only for their GXP BBs or BB30s.
So unless my bike is a BB30 or GXP 24/22, is it worth switching out my current BB for theirs?
Will it create more problem than its worth?
Or is it just a straight swap of the BB from a Shimano Pressfit on a Canyon bike to a GXP 24/22 BB installed into the Canyon bike?