- People want to live here. Not everyone of course, but if you're young, like a diversity of entertainment options and people, good food, culture, etc (yes - there are downsides). Very few people in the world say "I'd love to live in Boston, Seattle, Portland, etc for a bit to see what it's like". NY has that effect on people.
- Major companies and industries which are being disrupted or enhanced by technology are HQ'd there. Advertising, financial services to name two. If you roll in CT and NJ, you have insurance, pharma, etc.
- Lots of people so if you're doing something on the consumer side, many guinea pigs.
- Lots of money and influential folks here. The whole 1% thing.
- More and more VCs are setting up shop here as well. I think they see a good ecosystem here, and I think many of them don't mind having an excuse to visit NY for business.