Why can there only be one moveout thread?

The documentation seems to imply that increasing the MAXCONCURRENCY setting for the TM pool only results in an increased number of mergeout threads. Why can't there be more moveout threads? Having multiple cores doing the sorting, encoding and compression work that needs to be performed while moving the data out to disk could be really inrease performance (loading rates) when a lot of data is being trickle-loaded through the WOS.