As Engadget Japanese has noted, that makes them convenient for traveling, since you’ll simply have to find a local carrier and then enable your plan of choice over the internet. No need to swap out physical SIM cards or to rent pocket WiFi devices. That said, the technology is pretty young, and there’s always a chance that the place you’re going to doesn’t have a carrier with the option. You can check for eSIM and Apple SIM coverage on the company’s Cellular page.
Apple seems to be expanding its support for the standard in recent years. The iPhone XS, iPhone XS Max and iPhone XR also works with eSIM options, though they’ll have to be unlocked if you want to use two different carriers.