When traveling you can pre-purchase an E-SIM and already have it loaded to your phone in advance of landing - avoiding the whole airport SIM purchase shuffle, or the holding off on using your phone until you get to a convenience store, etc.

I use an E-SIM for my personal plan, saving the physical SIM for a work line.

Yes, eSIMs are much more convenient plus phones can have multiple. While I’ve never tried the multiple eSIM feature, I find it so much nicer to set up a new eSIM online than to have to deal with a physical SIM from a physical store. It’s also more convenient when getting a new phone, at least for iPhone. The setup can just transfer the eSIM from one phone to the next so your number gets moved with no effort on your part

From the phone manufacturer, it's fewer traces and less mechanical design work.

From the carrier side, it requires you to have their spyware installed to register the Sim

From a user perspective, someone can't just steal your Sim and put it in another phone

Somebody can't steal your phone and pull the SIM card out so that it can't be tracked.

As long as you don't have the ability to enable airplane mode or disable cellular data from your notifications shade, you can't stop it from being tracked if it's stolen unless it's physically powered off. And as soon as it's physically powered on again, it's immediately trackable.