FWIW: I explicitly do a full subcode check with cdrdao on every disc I rip and include the full results in the cuesheets, including all flag settings (set/unset) and the presence/absence of UPC/EANs and ISRCs. In the roughly 1000 or so discs I've ripped with this workflow, just over 45% have ISRCs, 4% have all-zero ISRCs, and the remainder have no ISRC whatsoever.
My collection skews older, but in my experience it's unusual for a recent CD (say, post-2000) not to have ISRCs, and those where they ARE missing seem mostly to be either true indie releases (nothing I own from Italians Do It Better have them) or DJ mixes/compilations (including soundtracks in the latter category).
Weirdly, I also come across titles with Digital Copy Permitted that you wouldn't expect. The Yello remasters all have it set, for example.
My collection skews older, but in my experience it's unusual for a recent CD (say, post-2000) not to have ISRCs, and those where they ARE missing seem mostly to be either true indie releases (nothing I own from Italians Do It Better have them) or DJ mixes/compilations (including soundtracks in the latter category).
Weirdly, I also come across titles with Digital Copy Permitted that you wouldn't expect. The Yello remasters all have it set, for example.