I've noticed that as I progress through the fantasy mode in this game -- very rarely do CPU players NOT resign with their teams. It appears the only time it occurs (at least in my experience) is when a relatively highly rated player is getting old and within a year or two of retirement. It may also have to do with who is in the free agent pool in that same position.
I tried messing with the LOWBALLED rating. It seems to take values 0 to 9. I couldn't see that it produces any effect, at least not if you edit it in a playoff.DBF and then roll over to the next season with it. The values are set back to zero at the start of the next season, so it may only be edited internally by live during player negotiations. Didn't seem to make any difference.
Any ideas?