Biopace was intended for all those novice and casual riders who ride around at 50 rpm or so, often with the chain on the smallest cog in back and the middle chainring (or the small chainring of a 2X crank). It's great at low cadences.

Shimano's fatal errors:

One, not telling bike dealers the idea behind the design.

Two, getting greedy. They forced all bike manufacturers who wanted to equip their models with Shimano groups (below Dura-Ace, anyway) to accept Biopace cranks. No substitutions.

I attended a Shimano seminar back then where Wayne Stetina, former National Champion on the road and newly hired Shimano marketing manager for the USA, was touting the wonders of Biopace. He was interrupted by Alex, a local Baltimore bike dealer. Quoting more or less accurately:

Alex: Wayne, do I understand this right? I won't be able to buy Shimano-equipped bikes for my customers next year that don't come with Biopace chainrings? A customer comes in, cash in hand, looking for a nice bike with round chainrings, and what am I supposed to tell him?

Wayne: Well, I hope you'd explain the benefits of Biopace. It's more comfortable and efficient and . . . "

Alex: Wayne. Wayne. You're not listening. I said "Cash in hand."

Wayne (politely): I guess you'd have to sell him a different bike with different components.

(Alex stares, theatrically incredulous.)