divorce - Why is it often Claimed a Forced Get is Invalid?

I've read that part of the problem of agunot ( women who are refused a divorce ) is that if we force the man to give a get then the get is invalidated, and thus Beitai Din in Israel refrain from using force.

However, that is not strictly true:

A most basic rule in Hilchot Gittin is that a Get must be given (and received by the wife, post-Cherem d'Rabbeinu Gershom) of one's own free will. (Rambam, Gerushin 1:1,2) If the husband is coerced, the Get is invalid. (Rambam, Hilchot Gerushin, 220[sic]) The oft-quoted dictum kofin osoh ad sheyomar rotzeh ani -- "we coerce him until he states 'I want to"' -- applies only in cases when (a) specific grounds for that verdict exist, (b) the Bet Din renders a verdict of kofin (we force him), and (c) the coercion is carried out by the Bet Din or others implementing its verdict.

We see that a Beit Din has the authority to coerce the man to give the get, and we can see from Rambam in הלכות אישות פרק טו, ב regarding a marriage without children for ten years that the Beit Din physically beats the husband till he gives a divorce (or takes a second wife).

In light of that, I don't understand why it seems that Batai Din refuse to use force in cases where the husband uses the refusal of a get as a means of blackmailing his wife, and where the claim of the Get being invalidated by the use of force comes from.