Trev,
I guess a good way to illustrate this idea would be to point out that if a perp wants sex, abusing children isn't exactly the safest or easiest way to get it. There's something more that the perp wants - a LOT more.
Perps seem to want power, in the same way some people thrive on throwing money around, driving an expensive sports car, owning a gun that can waste a forest in one shot, etc. For the perp, the ultimate kick is forcing a child to give up the one thing he would least like to give - sex.
The compulsive aspect of the whole thing can be seen in the fact that perps abuse time after time. Some of them molest hundreds of boys over a lifetime. They return to abuse even after being jailed.
Yes, it's sick, but there's the nature of the beast.
Much love,
Larry