Most people grow pot (at least the first time) from seeds they find in the pot they buy.
This is getting harder as more growers discover how to grow sinsemilla. Sinsemilla means no seeds, it comes from unpollenated females.
In '67, when I looked at the very first marijuana I bought ($10 for an oz. of Alcapulco gold) I saw seeds, and my first thought was "Hey! Now I can grow my own!"
The next morning I dropped my first seeds, I've been growing ever since.
The pot you grow from seeds you find in pot you buy will usually be as good as the pot it came from (but not always).