It's a shocking trend and almost always the main reason is the location of the restaurant in question.
Yes, it can be a saturated market and yes the competition is fierce but ultimately it's down to thos ethree magic words your estate agent will be so fond of using "Location, location, location".
What You Can Do
Quite often we come across clients who serve what in our opinions is the best food we've come across for that particular cuisine or location (yes, it's a hard job but we do try and visit our clients and dine there when we can). The reviews speak columes and all they REALL need is to be found.
Be Found Online, Be Found In Real Time
One of the things we specialise in is helping restaurants be found. You know, those little out of the way places that serve great home made tapas or that fish restaurant that serves freshly caught Calamari. Well we work with them to ensure they get the traffic they deserve.
By working closely with our clients, monitoring their traffic and advising them on how to get the most out of search and social we see their business increase.