Have you ever gone to your favourite restaurant or bar to find out that it's full and decide to go for the one next door? There are many businesses that position themselves to be the alternative after the popular choice. In order to be the next best thing for your customer, you need to be easily accessible and ideally be at the same place as the best. This is why you see businesses of the same type tend to open next to each other. It makes the location the place to be and improves patronage for everyone in the area.
Obviously, it would be better to be the best in your trade if possible but sometimes being the alternative is a viable strategy as long as you are at the right place at the right time.