What is slow play? Slow play is an effect. The causes have mostly been described already, but IMO are, listed in order of importance:
1) At public courses, management practices dominated by a focus on revenue generation at the expense of what Charlie calls "fun" and a consumer that is tolerant of slow play. I personally would rather pay more, see fewer golfers on the course, and play faster. It seems like most people would rather pay less and wait more.
2) At all courses, poor course design and setup--designs (which could be described as poor), like Erin Hills, or course maintenance practices, that make play at a good pace improbable.
3) At all courses, inconsiderate golfers. It's startling to me how few golfers understand the concept "be ready to hit when it's your turn." Pre-shot routine? Please, take it to Q-school pal, you're putting me to sleep.
For my part, I have found that when play is taking a lot of time (i.e. everyone's playing slow), changing my expectations and habits goes a long way toward increasing my enjoyment.
Charlie, this attitude is a slippery slope to mediocrity. Do you want to pay $50 for a bottle of wine, get swill, and "change your expectations" of the winemaker so that you'll enjoy it more?
Slow play is not an unsolvable problem--don't architects, course owners, and supers have the tools to make an impact (to the good or bad!)?
And consumers can vote with their dollars....