I do get why street photography is so popular, even though I am not a big fan of this genre. When I share my photos with close friends and family, they are immediately drawn to those photos that show other people. They study these photos intensely, stare at them for minutes, talk about them! When they see a perfectly composed landscape photo, they quickly glance at it and move on. Nothing to see there for them.
There are a number of reasons why street photography is so popular:
1) Most people are fascinated by other people's lives and street photography opens a window into other people's lives and conditions, albeit very briefly.
2) Humans like to be in social contact with others and if you are out in the streets among countless others, you may get a (false) sense of belonging. Most other fields of photography don't have this social environment while you take pictures (e.g., landscapes, outdoor, wildlife photography). As a photographer, you take your viewers with you, to the people into the pictures, and all are feeling part of the same.
3) It is so easy to do: you just go out in the streets, snap some pictures, and voila, you are a "photographer"! 🙄 It is one of very few fields of photography with instant gratification. The results are then amplified by social media, which are a perfect platform to share street photography.
None of the above says anything about the quality of the photos, of course, but it might explain the popularity.