Parallel Track function in GPS?

Yesterday I played with the parallel track function in the CNX-80 for
the first time. I was introducing the CNX-80 to a student and I had
planned a VFR flight via airways. My student (rightfully) questioned
the wisdom of an over-water segment, so we decided to fly that segment
on a 5-mile offset parallel track (it got us over land and was a good
excuse to explore a software function I'd never used before).

But, here's my question. Why is it in the box to begin with? Other
than the gee-wiz marketing value, is there any real practical reason for
it existing?

VFR, we didn't need it (it was easy enough to follow the coastline
visually). IFR, it would have put us outside the airway boundary, so
it's probably not very useful there either. Is "fly parallel to V157
offset 2 miles to the left" something that I might ever expect to get in
an IFR clearance if I file /G ?