Many bands, probably most if not all, begin their lives / careers doing pub gigs getting folk onto the dancefloor doing covers. Of course I am only talking about musical bands who actually play instruments and make music, not talentless, voiceless teeny-boppers who get signed on to a record label cos they got nice tits and make generic tripe aimed at 12 year old girls.
So anyhow, these bands later have their own material and have sold a few records. But they reminisce about the days when they filled a pub dancefloor in a smoke filled, crowded room with sticky carpet. Perhaps they long for those days, perhaps they think that if they make an album of cover songs then it might bring back the glory days of their past.
Perhaps I am full of crap.