A box of breakfast cereal might cost $5 and it could contain about a dozen servings. A restaurant breakfast might cost $15 and it would deliver exactly one serving (unless it’s an all-you-can-eat buffet breakfast :-) ).
A box of cereal is fast and cheap. This is good when it’s just you or you’re in a hurry.
A restaurant breakfast costs more but you can have whatever you want and it’s made to order. This type of breakfast is perfect when you’re trying to impress someone.
Stock pictures are like a box of cereal. Custom photography is like a restaurant breakfast.
Stock photos are fast and cheap. This is okay if your web site, brochure or other usage is only for yourself. But this is not okay if you need to make a good impression on someone such as your customers.
You wouldn’t serve a box of cereal at a business breakfast, so why would you serve stock pictures on your business web site?
There’s a saying that you should write to express, not to impress. But if you do a good job of expressing then that can lead to impressing.
The same thing applies to the corporate photography on your company’s web site. The pictures must first express something positive and genuine about your business. Only then do you have a chance of making a good impression and looking like a champion.