Is bullfighting still legal because of traditions?

Essentially, yes, bullfighting is still legal because it is considered a tradition and an essential element of Spanish culture. 

In 2016, when Spain’s constitutional court overturned the ban on bullfighting in Catalunya, they described the sport as “one more expression of a cultural nature that forms part of the common cultural heritage.” 

The more cynical opponents will argue that continuing the practice is more about financial benefit than a deeply held respect for cultural tradition, however.