The first freebies I gave away were f2s I made of seeds that I thought were discontinued by the maker, who then decided they were not discontinued.
The next were Orgi F2s that I had a huge amount from the pollination, and a lot of F1s had been sold. Copper Raspberries were next, and used because they sold very slowly when initially released and I had quite a few.
Citrus Blast was made specifically to be a freebie strain.
I'm about to send the next reg drop to DCSE with two fem seeds attached - Cob's Copper Candy [ last of these] - simply because I have nothing else left. I always liked getting bonus seeds, but I've often bought packs when none were offered.
Maybe if they come from a big seed bank, but it would be foolish imo to send out subpar seeds with a brand name on them, free or not. I got 4 TGA seeds from Attitude a decade ago, which resulted in me buying at least a dozen TGA packs because of the great plants I got free.