Generally it's a combination of both.
At least that is what I have seen.
It's one trade of say the Max Bemis Moon Knight will lead to reading the 2006 run and so on.
It really comes down to this-how much access does one have to all the trades if they are going the library route or the used book store route.
More folks target the used book market route.
For someone like Batman-he gets so much stuff in new editions-someone will just buy a new copy.
For someone like Static-the used market is pointless. Do you know how much trades with Static were going for in the used book market at one point-even the bad new 52 trade? $70 at one point for Milestone Brave and Bold trade.
While someone like Carol Danvers, Moon Knight and X-Men-I bet they have larger used copy sales for certain runs.
That would be great but the fandom is so mainstream now to where it makes it feel like they don't need to. Between all the speculations, fanfics, and the sheer amount of content being pumped out the comics feel like an afterthought.
Now what would be cool is if Marvel/DC could give out free stuff during premier weeks like pokemon and yugioh movies did when I was kid.
Reading List (Super behind but reading them nonetheless):
DC: Currently figuring that out
Marvel: Read above
Image: Killadelphia, Nightmare Blog
Other: The Antagonist, Something is Killing the Children, Avatar: TLAB
Manga: My Hero Academia, MHA: Vigilanties, Soul Eater: the Perfect Edition, Berserk, Hunter X Hunter, Witch Hat Atelier, Kaiju No. 8
Also they already heard how messy the comics characterization, continuity (or lack of thereof), relationship and lack of character development from the fandom (and how the plot jump from book to book). Some people active in the fandom because they fall in love with the simplified fandom version of the characters, and disappointed when the comics are not like that. So they decided not to read/buy and just enjoy the fandom version. It fits their taste already and it's free. They're a fandom of the fandom, shall we say.