"We couldn't release a double album and we were on deadline," the guitarist said of the 1978 recording. "Sometimes you're really getting into tracks you want to finish, but they don't make (it) because time was up."
Now many of those songs will be included when the album is re-released on Tuesday as a double disc with previously unreleased material. A box set from the album also is being released.
Mick Jagger said "Some Girls" was a pivotal album for the band.
"The records that came before this were not as good. This was better," Jagger said, referencing the heavily produced "Goats Head Soup," and "It's Only Rock and Roll," which preceded it.
At the time, punk rock and disco were threatening the old "dinosaur rockers," as Richards said, so the band had to get back to its basic stripped-down sound.
"The punks started to kick us ... the Sex Pistols, and The Clash, and other bands were coming out and we realized we were already in a second generation," Richards said.
One of the album's biggest hits, and also the most criticized at the time, was the dance track "Miss You."
"It's not like we wanted to make a career out of disco; it just happened to be that beat, and Mick came up with this beautiful idea. If you're ever gonna do disco, you got to do it now. It was like a one-off," Richards said.
Jagger, who says he loves all forms of dance music from the 1930s to house music, didn't know why it mattered.
"I never thought for one minute that people would criticize you for doing something with a dance beat," Jagger said. "So the idea of it being `Bob Dylan going electric' never occurred to me."
The song went to No. 1 on the Billboard chart, and spawned a variety of dance mixes.
Next year, the band will celebrate its 50th anniversary, and there's a great deal of speculation as to whether the band will tour for their milestone.
"I'm hoping to do something about it. Right now, I don't want to go too much into it. I'm pulling the boys together and (will) see what happens. It's a work in progress. I'm not Nostradamus on this, but we all want to do something for the big 5-0," Richards said.
All Jagger would say is that "we have a lot of things planned, who knows what will come to fruition."
According to Richards, he and Jagger recently mended fences after Richards revealed too much about his songwriting partner in his autobiography earlier this year.
"He's a brother, a best friend, and probably the most contentious person I know. All collaborations are like that. Nothing goes totally smoothly, but we always patch it up. We patched it up now. The thing is we enjoy working with each other; it's the idea of it that's frightening," Richards laughed.
The duo has written most of the Rolling Stones music, and though Jagger usually sings them, Richards does have his signature tracks. Among them is "Before They Make Me Run" from "Some Girls"; it has become one of his favorite songs to perform.
"It's pretty autobiographical. ... I was feeling a little hounded, so I think it came out of feeling that. I was on the run, basically. Very few countries would accept me at the time," said Richards, who was facing a potentially long prison sentence at the time because of a heroin possession charge in Toronto.
Other major hits from the album include, "Shattered," the Temptations cover of "Just My Imagination (Running Away With Me)," and "Beast of Burden."
While Richards said the unreleased music was ready to go, Jagger did say he tinkered with the remixes.
"'Claudine' and `Tallahassee Lassie' were all more or less as (they) were. I just listened and said, `Do they need a bit of percussion or a harmony vocal?,' but apart from that they're fine," Jagger said.
Richards is just happy that the band gets to release "Some Girls" with the songs they wanted to include.
"In a way it's interesting to put the head back on the baby," Richards said.