This is probably the best reason why you should start advertising on Facebook. People spend a huge amount of time on Facebook and they engage with the contents. They "like", "comment", "share", "watch videos", and, most importantly, people promote a lot of products and services with their friends and followers.
If you manage to get one customer from an Ad and you do a good job in taking care of that customer, expect ten more customers from him. Facebook took the power of word of mouth and multiplied that by the hundreds.