I thought eSIM was a downgrade

I thought eSIM was a downgrade — now I finally understand why carriers pushed it – MakeUseOf
Years ago, phones had slots for SIM cards, tiny cards that contain all the necessary data to connect to your cellular carrier. You could take the SIM card out of the tray and insert it into another phone or swap the SIM card for another from a different country while traveling to use a different number.