That's the simple test of a bureaucracy that has lost its way.
If your employees can't answer how something they do helps the customer or the company, you've insulated your people from their jobs.
"It's our policy," is not an answer to why. Saying the policy again, louder, is not an answer to why.
Their inability to answer this simple question might be because you haven't taken the time to teach your people how to think about the work you do. Or it might be because you're hiring people (or rewarding people) who don't want to think about your work.
Don't you want the people who do the work to understand it? And don't you want your customers to feel respected by the people who serve them?