One reason might be that he believes his situation is somewhat anomalous compared to others using the same software without excessive loads - and that it might be easier to tune his install rather than force 200 active users to 'try another forum' just for the hell of it.
OK, maybe the OP doesn't feel that way, but I do I've got hundreds of dollars and thousands of hours invested in licenses, custom skinning, three years of community development, painstaking education of non-savvy users in the ins/outs of the current software. I personally love trying out new software and basically try everthing, and often. But it's a different matter to move a live and thriving community. Particularly if there might be some tweaks available.
Unfortunately, I don't know of any so hope to learn something myself, here