Dakota makes some good points:
"the various bodies that sanction fastpitch need to either get tough with umpires on the crowhop / leap rule, or they need to modify the rule to line up with how it is being called ... snip ... To continue to have a rule that the majority of umpires refuse to enforce (for whatever reason) or don't know how to enforce is not good, and hurts the integrity of the game and the officials", except that lining up the rules with how it is being called would take about 25 pages of zig-zag lines.
I see some factors to overcome:
1) illegal pitches are judgemental and require training and focus
2) each rule body defines them a little differently, even those that require the same number of feet on the plate
3) coaches will always argue "she's been legal for 99 years", "no one else calls that", etc.
4) certain umpires seem to think it's a macho thing to "let them play" or that the "best call is always a no-call"
5) the constant lack of calling them has gained momentum to the point that umpires don't call them because they get negative reactions from other umpires for disrupting (i.e., lengthening) the game or because they get negative images in their associations and future assignments
6) the coaches and players understand the rule even less consistently than we do, partly our fault, mostly not caring