I'm growing bagseed because I'm waiting for my good seeds to arrive. Genetics play the most important role in how your cannabis comes out. A lot of times seeds get in your bag because some plants herm'd. So already you're starting "your strain" with poor genetics.
Not to say bagseed is always bad. Look at ChemDawg (ChemDawg 91', ChemDawg B, D, etc etc) ChemDawg found seeds in a bag of killer pot. He grew it out and bam ChemDawg is born (which led the way for OG Kush etc or so I've read)
Interesting theory but for the most part the seeds are there because.in mexico where its grown harvested early packaged and shipped the cartels mix females with males and don't really give a fuck how good it is because they get $200 a lb lol