1. People want, & even need your product.
2. You make it easy for them to buy from you.
I walked a couple of miles around downtown Salt Lake last Sunday, hoping to find an open espresso bar. (Yes, there is coffee in Salt Lake.) We were going to the theatre, and wanted a place to enjoy some hot coffee before the show started. Sure enough, not a spot open in the proximity. Ask a business owner, and they will tell you there's a lack of traffic in the area, thus they would lose money being open. However, these same businesses are frequently spending much of their profits on advertising to get people into their spots.
It's possible that there are days when necessary foot-traffic is low. But this show had a nearly sold-out, 1800 seat matinee followed by an evening presentation. That's 3600 possible customers you could have attracted by simply being open.
This isn't a unique problem to one city. I walked past several closed restaurants in San Francisco one Sunday. Meanwhile, an outdoor farmer's market, and live music had attracted thousands of pedestrians to the area.
If all your competitors are closed on Sunday, or all close at 9pm, you can strike the winning punch by being the one to be open. Think about any consumer packaged goods company, they must operate their factories and produce more product to sell more product. There are reasons to be closed, but think carefully about when you should be closed. When you lock those doors, it's just like the cereal company being out of stock on a retail shelf. Don't let your customers walk up to your empty shelf by seeing a closed sign during a perfect opportunity to win them over.