Rich people have some rather interesting quirks, as many Redditors will attest to. However, one multi-millionaire has a surprising reason as to why he is picking up passengers as a driver for UberX.

Paul English is a co-founder of Kayak, a popular search engine for travel deals, and an Uber driver behind the wheel of his Tesla S P85D, which retails for over $100,000.

English served as CTO at Kayak since its founding in 2004 until it sold to the Priceline Group for $2.1 billion in 2013. Nowadays, when English is not teaching entrepreneurship courses at the Massachusetts Institute of Technology (MIT) School of Management, he is working part-time as an Uber driver in Boston.

Since he began driving for Uber on Oct. 31, the MIT lecturer and billion-dollar company founder has picked up 26 customers in his car. The reason, he says, is to do research for his new startup. He told Inc. during an interview:

“We’re rethinking how people book travel, from how they conceive travel, who they get advice from, where to go, how much work it takes to book it. I always said even when we were at Kayak that we sucked less than other websites. I was trying to make it simple, but even with Kayak there was some work involved.”

His objective as an UberX driver was to get an idea of Uber’s user rating experience. English explained:

“I wanted to study what it felt like as a driver, knowing that at the end of every ride, you were rated on a scale of 1 to 5. And the drivers rate [passengers] as well. … [They’re] trying to reward kindness. I think that’s been really good.”

Since his noncompetitive contract with Priceline expired in July, English has raised $20 million for his new incubator called Blade. Their single focus is to create the next great travel company, according to English’s LinkedIn page.

In testing Uber’s rating system, English said he has given five stars to all but one abusive and angry passenger. Retelling stories about his passenger experiences, English said he had picked up a group of people and driven them to a downtown nightclub in South Boston. He recalled:

“They’d been drinking, and I can’t replicate her Boston accent even though I had one, but she looked at the 17-inch screen and said, ‘You must be a millionaire!’”

He said that In only one incident did passengers know who he was:

“When people ask me what I do [for a full-time job], I say I’m a programmer. I don’t want to talk about me; I want to learn about them. But I picked up this couple about 25 years old, and one’s showing an iPhone to the other, and then one of them goes: ‘Are you Paul English?’”

English explained that he enjoyed driving people around and found it fun chatting with people he probably wouldn’t have run into any other way. He probably won’t stop driving for Uber anytime soon either, as he said:

“I wouldn’t be surprised if I still do this a year from now. In my day job, I’m a CEO. Life is different when you become a service person and the customer becomes your boss.”