So this video is making the rounds of the YouTubes- an OfficeMax flash mob took over Union Square in NYC via subway and bus and did a huge dance routine in front of pleased onlookers.
This is the sort of frivolity that is enabled when you have vibrant street life. This particular example was enabled by a corporation, but ImprovEverywhere is all-volunteer and all-amazing, and mostly NYC. They're also the group responsible for the pantsless subway ride.
Aside from impromptu musicals, vibrant streets also enable such wonderful things as street musicians and street food. Steps from where that elf video took place, my friend and I sat for nearly half an hour and listened to an amazing jazz trio, at around 10pm. And street food? Most amazing thing ever. There is inexpensive, delicious food literally everywhere you turn in New York. And not just junk food- open-air fruit and veggie markets were liberally sprinkled throughout the city. Street food vendors are illegal in Los Angeles, and heavily regulated in Riverside.
The point is that walkable, transit-friendly spaces do more than just allow you to get from place to place- they allow you to enjoy a bit of culture on the way, something you'd never get while driving through.