The Betamax may have been a great VCR, but it was a flop. Sony wouldn\'t allow any other companies to make VCR\'s with that format. Very shortsighted on their part. VHS on the otherhand became very popular because other manufacturers were allowed to make it.
Also the price was a problem too. Since you had a variety of brands to chose from with VHS it was more affordable. Call it a marketing blunder, but it was still a failure. Sony has learned since then in some respects, but occasionally Sony reverts back to its former practices ie not licensing 3rd party accessories such as memory cards for the PS2. That is just idiotic.