It’s been only the last year or so that people have been trading and gifting in mass, say two years ago people still traded or gifted seeds but I’d say it was 1/20th or less the amount of right now.
As for strains becoming popular really they just come and go as the flavor of the season.
Whether say goji og, ghost roses, dark sparks, tut crosses or whatever one thing you’ll see is what’s typically given out in volume is what as becomes popular or at least grown for a bit.
Or at least my observation.