Geometry primitive Points don't have a *Curve Parameter*. 

Unless the attribute is captured while the geometry is still a curve, it will evaluate to 0. 

Here, the *Curve Parameter* is manipulated before capture.. you could do it afterwards. 


[![enter image description here][1]][1]

As requested, the attribute is captured on the (implicitly) evaluated _sample points_ of the curve, at capture-time. Thereafter, it is linearly interpolated for other entities occupying that field, that are on the same (green) Geometry branch of the tree.

[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/tf0mh.png
  [2]: https://i.sstatic.net/isiac.png