Me neither and i wonder why.

There really should be no reason.

I had to throw away many perfectly good power supplies when upgrading the graphics cards because they had not enough pins. So i would count out economic reasons.

Many 3d Printers started to convert to 24v recently because you have thin cables and overburdened plugs for high powered heaters and stepper motors. That caused no issue either it is amazing what modern voltage regulators can do.