Locals are commonly a poor source of good information. I definitely wouldn't use them as an exclusive source. I make it a habit when going to the other side of town when running an errand to ask the teller where's a good place to grab lunch. More often than not they'll point to something like a Subway or KFC across the street. Their priorities are generally something quick and cheap.

It's just too easy to live some place and not seek out the unique, locally available things. Many times when visiting other countries the people working there have never done the main thing people visit that area to do. Also tastes vary greatly. These apps offer an aggregate or editorial filter for something instead of a sample size of 1.