Warp was a threshold for the Federation introducing themselves to new friends, and admitting that aliens exist everywhere else in the Galaxy, as soon as their new friends had the one tool they needed to head out into space and see for themselves that the universe is densely packed with life.
If the Federation didn't say "Hi, how you doing" as these friends are getting ready to head into space, in a week or a month, they'd meet in space anyway at a toll bridge, a weigh station, a neutral zone or a demilitarized zone.
It's like how you shouldn't buy a car, before you have your driver's license.