It was more of a rarity and taboo thing to hear rappers talk about it, as far as mainstream....but, even 15 years ago, you had Shyne, Beanie Sigel, Black Rob, Prodigy, Styles P, Andre Nickatina, Mac Dre, Three Six, BG, Juvenile, plus ALL the Houston rappers came into the game talking about lean... just off the top of my head talking about using coke, e, pills, shrooms, lean, heroin....It's become much more prevalent, evidenced by the fact nearly all mainstream radio rap song have a reference to molly, lean, or xanax.
My basic thoughts are just like anything it became more accessible, and everyone ran it into the ground....It was much more rare and head turning back then though.
Also, a generational shift in the dope game from the 80's/90s/2000's to the rise of BMF/Meech, all those guys were heavy on pills....rappers imitated and took cues, and came up under guys who would never fukk with coke, because of the stigma from crack, although obviously some did, it wasn't fashionable, so to speak. As this progressed, the old mantras and rules, loosely speakig, broke down, and now, the common stereotype is the Future model, leaned out out his mind, barred up, smoking blunts, moving bricks....as opposed to the controlled, mafioso type businessman Jay represented in the 90's...obviously different regions, but the point is fair, I think.