(NEXSTAR) – Have we reached a tipping tipping point?

If you regularly pick up takeout from local restaurants, or you start your day with a latte from your preferred coffee shop, you’ve likely been prompted to leave a gratuity after swiping your card at the point-of-sale machine, usually via a digital tipping screen with default dollar amounts or percentages.

Some customers may also feel they’re being prompted to tip more often — and in more scenarios — than in previous years.

“There are no good studies, but most people’s experiences are … they’re encountering these things more and more frequently,” said Michael Lynn, a professor of marketing and management communication at Cornell University and the author of more than 70 studies on the subject of tipping and tipping culture.

As Lynn explained, it’s hard to know for sure whether more establishments are accepting or soliciting tips than, say, a decade ago, when tips were more frequently collected somewhat implicitly (via a tip jar, for example). But the sheer number of anecdotal evidence Lynn has gathered gives him a good idea of how often consumers are being presented with the option to tip.

“I personally believe it’s more common,” Lynn told Nexstar, pointing to quick-service restaurants and coffee shops, specifically.

Etiquette expert Diane Gottsman, the founder of the Protocol School of Texas, feels similarly, telling Nexstar that she’s increasingly asked about proper consumer behavior when prompted with such a screen, either in-store or on an app (like those of Uber or Starbucks).

“We are subjected to that app, that screen, almost every day when we buy a coffee or a sandwich,” Gottsman said. “So we have to get used to this form of payment.”

Gottsman acknowledges that customers may feel guilty when presented with an option to tip, but Lynn points to studies that suggest it also makes people upset or even angry.

“People think it’s manipulative, they resent it, and their perceptions of service go down,” Lynn said, citing a recent study from researchers at Purdue and Temple Universities which found that, in a significant number of cases, participants who were presented with a tip screen had more “negative emotions to the payment experience” than those that didn’t — and those weren’t even in real-world scenarios.

So why do so many establishments appear to be ditching the tip jar in favor of a prompt via a tablet or app? To put it plainly, it’s because it might be working.

The same study by Purdue and Temple researchers found that, overall, a tipping screen was effective in “elevating tipping amounts” from customers who otherwise wouldn’t think to leave a gratuity. Another study of taxi cab riders in New York City found that tipping screens — specifically those with default options for tipping 15%, 20% and 25%  — had “a significant effect on tipping amounts.” When those defaults were jacked up (to 20%, 25% and 30%), the average tip increased even more, effectively making up for any customers who declined to use one of the default options out of frustration, researchers at the University of Chicago and Columbia University found.

But some studies on the subject came to murkier conclusions. One, published by authors at Murray State University and the University of Central Florida, found that customers at limited-service restaurants (where they paid before getting their food) were more irritated and less likely to return when tips were requested on lower priced items (say a $1 item), but didn’t feel as negatively when tipping on a larger check.

Another study published in the Journal of Business Research suggested tipping screens resulted in increased instances of tipping, but only when the server or employee was physically in the presence of the customer.

“’Guilt-tipping’ is what they are calling it,” said Gottsman. “We think everybody is looking at us.”

Lynn, meanwhile, believes employers at quick-service restaurants have reason to be fans of more explicit tip requests.

“It helps with recruiting staff,” Lynn says. “Especially in today’s environment, where there’s a shortage — even quick-service would have a hard time recruiting staff [at places] where these employees, these baristas are getting regular minimum wage, at least.”

Speaking with Nexstar, both Lynn and Gottsman pointed out that servers at full-service establishments are likely making less than minimum wage, meaning they may be more reliant on tips than employees at quick-service eateries or shops with counter service.

“We have to remember that if you are sitting at a table, at a restaurant, that gratuity is socially mandatory,” said Gottsman, who clarified that she’s “pro-tip” in most situations. “That [server] is working for a tip … and that offsets their income. But if you are standing at a counter, at a deli, this person is working for an hourly wage. Maybe not a large hourly wage, but an hourly wage. Tipping here is a courteous gesture, but not required.”

“Tipping is voluntary and you should feel free to say no,” added Lynn of leaving gratuity at food-service establishments where employees make more than minimum-wage. “Outside of the restaurant context, most people wouldn’t tip.”