I noticed the webpages for many rural hotels (Hampton Inn caliber) indicate free shuttle transportation within a small radius.

I've only ever used such service in groups, organized by an event planner, and I have never seen anybody tip the driver, who always seemed to be a random hotel employee.

This leads me to 2 questions.

1. Are these free hotel shuttles intended only for groups/professional events, or are they also suitable for, say, a solo traveler just going to a restaurant across town?
2. During solo travel, what is the tipping custom -- how much, and when?