I realize that I have strong opinions about this and motivation for doing so, but I really believe every word that I'm saying. I believe that stock photos have only very limited applications and are are a smart choice in only very limited situations. (They're excellent for making sub par businesses look as good as an average player in their industry.) To show my sincerity in all this, I've never submitted a single image to a stock photo agency in my entire 35 years in business as a photographer. During this time, many other photographers were telling me that I should be doing this to earn additional income. (And I could have really used the money at the time.)
Use them at your own peril. Most people can tell that they're stock. They don't inform. They don't make you look unique. They don't inspire trust, they undermine it.
In short, they make you look second rate.