Excluding about a thousand 8 track cartridges, at least 90% of the 1,000 CD's and 3,300 vinyl albums I have are by bands that never made it. They may have been popular in some region somewhere but that's about it.
In the 70's & 80's, I figured the heavy hitters that had their songs ceaslessly played on the radio did not need my support so generally, I did not buy those records or CD's. I could only hear Led Zeppelin, Pink Floyd, Eagles. Fleetwood Mac, etc, etc, etc on the radio so many times before they got boring - played to death you might say.
I am less discriminating with 8 track tapes. I take what I can find as long as it it's rock, blues or R&B and not knowingly a duplicate of something I already have.
When I dwell on the thought, it baffles me somewhat that a group (or artists) can be absolutely huge in the UK, Australia or Europe but are basically unknown in North America. Either their music was more important than the market or record companies weren't behind them.