Here's a good example of why it's important to know these things:

Lets say I'm interested in shooting 60#'s this fall....but I still want to shoot a mechanical BH.

Ya think it matters to know my KE? How would I decipher what that might be?

Yes....in some situations it IS important to know. If I were shooting 70#'s out of the 82nd....the point (RE: KE) would be moot.