Depends on what the computer is designed for. Imagine you want to parallelize up to about 16 nodes or 1000-2000 cores of a new xeon. And your code is not optimized for accelerators. Well you might build a large machine with hundreds of nodes, but with the intent to run many 16 node jobs at a time. The largest machines though mostly are aiming for jobs that use a significant fraction of the total machine and are chasing peak performance so accelerators it is. Also I didn't look too closely at the link, but some machines that aren't technically accelerators like K computer or the old IBM Bluegene computers are closer to general purpose accelerators than they are to fat xeon nodes.