Millions of rebuilds have been done without them and all the engines that have rolled out of Detroit since the beginning of time didn't either. But a torque plate can be a huge benefit. One way to look at it is if a block is not finished honed with a plate, when the head it torqued on every place a head bolt is close to the bore, the cylinders will have tight spots. So the rings will only contact the cylinder walls at those tight spots until sufficient wear occurs to wear those spots down to begin full contact so they can do their job properly.
