Punch line: the true reason behind this had to do with technology, engineering, and safety issues. But I can kind of hear David Lee Roth delivering the lines in his over-the-top screamy-voice when I read his quotes. Actually, I can hear David Lee Roth's voice when I read the rider.
Video below: "Jamie's Cryin," from David Lee Roth's bluegrass cover album of VH hits, remixed by a fan in a homebrew video with (why not?) a Popeye cartoon. You can buy the record here if you are so inclined: Strummin' With The Devil: Bluegrass Tribute to Van Halen.
Update: JKD says,
Also, a recent episode of "This American Life" also had a segment on
the brown M&M clause, and the general dynamics of touring and
contracts, with John Flansburgh from TMBG: