I don't find it streamlined at all. Having to enter an obnoxious amount of personal details, sifting through pages of dark patterns trying to sell you upgrades, addons, meals, extra baggage, insurance..., clicking through an extra step to say you don't want to hire a car or book a hotel, the seat selection page that tries to trick you into paying for a seat when you can actually just click "next" and get a free seat assigned, dodging paying "in your local currency" at an inflated rate when my bank will do it at the interbank rate. And that's if the airline's crappy site is actually working on that particular day and isn't crippled by some javascript error caused by mountains of front-end cruft.

Pass!