Yuri Artibise has ten answers:

While I mused that perhaps it is simply that Phoenicians prefer to hide behind block walls than interact in public spaces, other than at ‘official events’, upon greater reflection, this isn’t the case. Several other urban parks in central Phoenix are well used most of the year, notably Encanto (recently named one of America’s Best City Parks by Forbes) and Steele Indian School Parks, so if it isn’t the people, why other than the odd student and homeless person, is it dead 90% of the time?

His full list is here.