Dragonmarks do not require spellpoints to use - they are clicky abilities, which is why they come in handy on some builds.
The bigger issue is that pure Fighters don't have an option to pick up Extend as a feat, I believe. You'd need to multiclass at least one level of a spell casting class to get it.
To the OP's point of why they're not used more... They were nearly unusable for most of DDO's history; only recent changes have made them more user-friendly. But, even with the changes, they are mostly for niche or flavor builds. And I say that as somebody who has uses them often in my builds.