Even if you travel an e-SIM is viable. Your phone needs to be able to support at least two active SIMs or e-SIMs to be useful though. My Pixel has a physical SIM which has my home account and I use the e-SIM for travel so people can still ring me on the home number when I'm away.
I traveled to Thailand this summer and even before I left Europe I had bought and registered an e-SIM from DTAC for my trip. It had unlimited data and even a Thai telephone number. As soon as the plane landed I turned on the phone and it was active. As I walked into the arrivals hall I could have bought a physical SIM from the multitude of booths selling them but I'd likely have spent 20 minutes faffing around, registering and getting the SIM activated after an already long flight. But I would have had to take my home SIM out to use the other SIM which wouldn't be ideal. So the e-SIM allowed me time to research & buy the best plan for the trip and have it set up even before I left. There are also a lot of online e-SIM services which sell (mostly data) e-SIMs plans - Saily and so on - which are convenient but more expensive.
That said, lots of phones are still physical SIM only and some phone providers are way behind the curve selling e-SIMs. So a physical SIM is still useful and does have some benefits, but I don't think I would mourn its passing. My original point is I think Apple just removed the slot for bullshit reasons and it gimps the phone even more than it already is.