How often do Lyft and Uber customers tip their drivers? Maybe less than you think.

When it comes to having food delivered, Americans are accustomed to offering a gratuity. But it's a different story for people whose job is delivering people to their destination. 

Only some 28% of rideshare trips result in tips, according a recently released report by Gridwise Analytics, which operates an app that tracks earnings for 500,000 active rideshare and delivery drivers. 

For nearly a decade, Uber didn't enable users to tip, "and consumers have gotten used to not tipping for that type of service," Ryan Green, CEO of Gridwise, told CBS MoneyWatch. "We saw some of the high fares, when it's more than $1,000 but zero tip, and that's for six hours of driving."