Because it was hard to listen to lp's while driving down the road, and they sounded better than 8-tracks.
8 tracks
There are 8 tracks on Lady Gaga's The Fame Monster.
1998
Tracks Ahead - 1990 FairPlex Garden RR 8-8 was released on: USA: 2012
1985
Reel Dudes - 2012 Stop Being So Paranoid 1-8 was released on: USA: 18 July 2012
8-track tapes were introduced in the late 1960s and became popular throughout the 1970s. Their usage peaked in the early 1970s, but by the late 1970s and early 1980s, they began to decline in favor of cassette tapes and other formats. By the mid-1980s, 8-tracks were largely obsolete, although some collectors and enthusiasts still appreciate them today.
8
8 Sides on a Stop Signsides on a stop sign
Tracks Ahead - 1990 The Mollibahn 8-7 was released on: USA: 12 November 2011
Tracks Ahead - 1990 The Flying Yankee 8-5 was released on: USA: 2012