There are plenty of misconceived thoughts photographers have when working with lawyers, doctors or CEO's of large companies, but the number one reason? TIME! You as a vendor need to access what the business is, who the people are, what are their positions, and their personalities. Once you take all of that into account then you can determine the "time" needed to be spent with them. It's a sliding scale. Some clients need more face time to feel as if they are getting what they need. Others just want it to be over with and their time is more valuable than working with you to create visual assets.
So the bottom line is TIME! Understand who you're working with and go from there. If you're taking a portrait with the CEO of a Fortune 500 company, your time spent with them should be 15 minutes max. Have your set ups predetermined, lighting perfecting and make it happen. Respect their time and move on. They'll appreciate that more than you think.