I'm not a musician, but I've seen plenty of DJs setup their gear. It is clear that the connectors and cables are designed to be physically durable. They work in environments where even a beefed up USB cable would only last a few gigs, since building compact connectors for consumer grade electronics is at odds with the day to day reality of commercial applications.

I'm sure that other factors play a role. The economics of going digital would be terrible if it meant replacing a significant amount of equipment every time a new standard took over the market. Again, pointing to USB (since that it what everyone seems to associate with universal digital connections), we have seen three major iterations and a number of minor ones over the past 30 years. That's hardly the type of cycle that businesses want to hop onto given that a tiny operation requires thousands of dollars of equipment, where any given component may be anywhere from a couple of years old to over a decade old.