@Debra300 Most people I know do this because, after searching for flights in a regular browser, we've found that when you go to book the flight you've chosen, the price has gone up! I prefer to fly Delta whenever possible, but I first search on Kayak to get all available airlines' times and prices. Then I go to Delta to book. When I've done this on a regular browser I've found that the price was higher than originally stated. So I start with Kayak in an incognito window, narrow it down, log in to Delta and book.
It's interesting that airlines have figured out how to raise the price on you in this fashion, while Airbnb will tell hosts that, on the one hand, people are looking at your place and, on the other, you should lower your price to attract more bookings. I don't necessarily want Airbnb to do this form of bait-and-switch, but sometimes I wonder about their grasp of supply and demand economics.