Grain free is taking over?

After researching pet foods it seems like almost 90% are now grain free. Is this just a fad?
I’m aware that upto 1 in 10 dogs suffer from allergies to grain, but going by this you would expect 10% of dog food to be grain free not 90%
I spoke to my vet about it and he said, unless you know they have a grain allergy, it is best to avoid grain free.
I’ve done some more research and the benefits of grain seem to outweigh the negative (especially if your pet isn’t sensitive).

a few quotes below I’ve come across while researching…

It’s a common misconception that dogs are carnivores. Actually, they’re omnivores, meaning they’re able to digest carbohydrates, like those you find in grains. 

Whole grains contribute important nutrients to your dog’s diet, such as vitamins, minerals, and fibre. 
A study by the University of California, Davis, found a link between dogs being fed grain-free and legume-rich diets and types of heart disease, known as taurine-deficient dilated cardiomyopathy (DCM).

Research is still ongoing to determine the biological processes at play, and how the affected dogs’ diets contribute.
“The FDA is investigating a potential dietary link between canine dilated cardiomyopathy (DCM) and dogs eating certain grain-free dog foods. The foods of concern are those containing legumes such as peas or lentils, other legume seeds, or potatoes listed as primary ingredients. The FDA began investigating this matter after it received reports of DCM in dogs that had been eating these diets for a period of months to years. DCM itself is not considered rare in dogs, but these reports are unusual because the disease occurred in breeds of dogs not typically prone to the disease.”