DC started that around 1979 and then ended it by 1984. They were great. The Adventure Comics stuff was terrific.
Meanwhile, Marvel had the short lived Pocket Book reprints around 1978. Great stuff too. DC did some black & white reprints in PB style. Okay but they changed so much of the art work... not so good.
The trouble with the DC digests was that they never has anything like a regular Superman digest or a Batman digest. They could've had a Superman digest, for example, which featured a couple of reprints of solo Supes stories, a Supergirl story, a JLA story with Supes in it, a Superboy/LSH story, and maybe a rotating non-Supes character (WW, Capt. Marvel, GL, etc.) Same with Batman. Or maybe a JLA digest with a couple of JLA stories with Flash, WW, GL, Aquaman, etc. as well.