I'm trying to understand what you are saying - are you asking why bullfighting is a fine art in their culture?
If yes - because it's a part of their history and their heritage. Every culture has different things that they have kept from their past and still treasure to this day.
OK , from where they take this sport ?
Here's what I found:
It dates all the way back to 711AD when the first bullfight took place in honor of the crowning of King Alfons VIII.
It is reported that each year, within Spain, 24,000 bulls are killed in front of an audience of 30 million people. The bullfighting season runs from March to October. Bullfighting was originally done on horseback and was a sport reserved for the aristocracy.
This changed when Felipe V prohibited the nobles from practicing the sport as he felt it was a bad example for the public's education. From then on the commoners took on the sport, facing the bulls unarmed, dodging and taunting the bull then eventually placing small spears into the bull, the origin of the banderillas of today's bullfights. Around 1724 the sport was transformed from horseback to foot. The bullfight is literally a dance with death. The bullfighter has to carefully examine and study the movements and strengths of the bull. One wrong move and he will end up gored or seriously injured.