Why don't Catholics eat meat on Fridays during Lent?

According to an urban legend, the pope, cardinals and bishops initiated abstinence from meat on Friday to promote the pope’s fishing business. That urban legend has no foundation. St. Peter, the first pope was a fisherman and Jesus said to the apostles “I will make you fishers of men.” (Matthew 4:19) Yet subsequent popes have had no financial or economic interest in the fishing business despite this bizarre rumor. The tradition goes back to the first century, when Christians abstained from eating meat on Fridays to honor Jesus’ death on the cross on Good Friday. Because Jesus sacrificed his flesh for the salvation of humankind, the flesh of warm-blooded animals wasn’t consumed on Friday.

From the book, Catholicism for Dummies by Trigilio and Brighenti