Because VHS released the rights to duplicate its products, more
people had the stuff, everyone wanted to exchange their videos
(like porn), so the most common won the battle.
Answer
VHS was licensed to many different brands. Many competing brands
had to lower the price to be competitive. Beta was only in the Sony
brand and did not lower the price to properly compete in the
consumer market, even though they had a demonstrably superior
product.
Video rentals drove the consumer industry. There were more VHS
units in the hands of consumers, therefore the distributors of
video released their products in the VHS format more than Beta.
Eventually Sony conceded the consumer market to VHS. For many years
Beta dominated the professional broadcast market because of their
vastly better picture.