But I agree selective breeding and providing optimum conditions for the particular strain will increase yield and potency, but it's only a major issue if you're growing commercially.
My parents and I made up for lack of yield (we tried to use what space we had playing the 'how many colas will grow in a 3 inch pot' game) with quantity. Some were ordered online, given by friends and some was bagseed.
Until I was about 12 I assumed the pot seeds were tobacco seeds, because no one in the house valued them all that much and my dad used rolling tobacco. I played with them and ate them when I was little, added them to art projects etc...