Flight Following question

So far, every time I come out of ROG and request flight following to it
doesn't matter where, I get a discrete squawk that allows departure to
hand me off to Memphis Center, or Dallas, or Kansas City. Coming out of
LIT however I've never been given anything except a local code and then
about 15 miles out the familiar "radar advisories terminated, squawk
VFR, have a nice day".

I specifically tested this twice on Friday, making sure that when I
called up clearance delivery and then ground that I made it very plain
that I was requesting flight following. Both times, again they dumped me
from the system between 15 and 20 miles out. The second time, I forced
the issue and stated that I was requesting flight following for the
enroute segment if able. I was then given a Memphis enroute code and
handed off within about 10 miles.

My question for the group is: is there a special terminology that should
be used when requesting full-enroute flight following? Or, why do some
controllers provide that service automatically and others seemingly only
under duress? (I don't think it is a controller issue, however it might
be a facility policy issue).