Why did the 70's Fantastic Four cartoon replace Johnny Storm with a robot?

Question

In 1978, an animated adaptation of The New Fantastic Four was released on television, only in this adaptation the character Johnny Storm (alias 'The Human Torch') was omitted in favor of a robot named H.E.R.B.I.E.

Was a reason ever given for this choice?

Answer 1

From https://comicvine.gamespot.com/herbie/4005-23720/

“In 1978, when the Fantastic Four was being made into an animated series, the character of the Human Torch was unavailable. Though a popular urban myth contends that the Human Torch was replaced out of fear that children might have attempted to emulate him by setting themselves on fire, the reality was that the Human Torch was one of the characters that Marvel had licensed to Universal Studios for a solo film (which never materialized). Universal was unwilling to allow NBC to use the Human Torch in the show, so that a replacement was needed.”

Answer 2

According to comic book writer, Mark Evanier, Marvel had licensed the rights to use the Human Torch in television to Universal Studios at the time, as part of the same deal which led to the 1978 The Incredible Hulk live-action series.

Universal Studios never actually made anything with the Torch in it, but nevertheless, they wouldn't allow NBC to use him in their 1978 The New Fantastic Four animated series.

Mark Evanier: “In 1977, Marvel made a deal that licensed a number of their characters to Universal Studios to be developed as live-action TV-movies and potential series. The Incredible Hulk TV show (the one with Bill Bixby and Lou Ferrigno) came out of that deal, as did TV-movie/pilotss of Dr. Strange and Captain America that never became regular series. The Human Torch was one of the characters that Universal wanted to develop, and a teleplay was written but never produced.”

“This meant that, the following year when NBC wanted to buy a new, animated Fantastic Four series, the rights to the Torch were encumbered. Universal - which was not to be involved in the cartoon show - would not make a deal that would allow the Torch to be included. Therefore, he was replaced by a robot named H.E.R.B.I.E., conceived and named by Stan Lee and designed by Jack Kirby.”

_{Comic Book Urban Legends Revealed #16!}