So you're saying special events, which are intended to attract crowds, are more vibrant when times when there is no special event? Perhaps we should just schedule never ending special events? This deserves more study...
In a way, getting rid of cars is the special event: increased foot traffic, food vendors, outdoor seating, and other events like markets and live music tend to follow on naturally.
Apart from pedestrian streets, you also see this in well-integrated urban parks and plazas like Union Square, Washington Square, or Bryant Park in NYC.