By the way, why would anyone glue /epoxy the end caps onto the hull pylons? Seems like overkill to me.
Racers do this to keep the frame stiff. A stiff frame is significantly faster - the energy that would be wasted iin flexing the frame is applied to making the boat go faster.
A new boat is pretty stiff right out of the boxes, but after a few years of use, it loosens up considerably. Gluing the castings to the pylons is a cheap way to re-stiffen the frame without buying a new boat.
Test to see how stiff your boat is: With the boat sitting on the ground, slowly lift one bow while watching the other bow. If you can lift it more than a couple of inches without the other bow moving, most racers would consider it too loose.
It doesn't make any real difference on a recreational level, although it can be unnerving to see the bows moving in different directions when going through waves.