Apple could pitch it as saving the world for plastic SIM card waste ( throw away electronics are bad. but buy a new iPhone every 2-3 years. ) . And don't have to put that Sim-card-tray-poker in the box.
It is more along the lines of dropping CD/DVD players and floppies from Macs. In part, it will be pitched as "you won't miss it". The default would be to just give folks the sim-less phone and the sim card model would be a special order for those out of the "norm" usages for them.
Some people switch sim cards multiple times a year and some folks never touch it for the lifetime they have the phone. Those folks this is a "big deal". But probably for a large number of folks it is a non issue. (so why do they need a sim-card version is as equally applicable viewpoint. It is a non factor so Apple doesn't need to 'sell' it as a feature. )
There is some security case upgrades in not having a SIM that someone could steal ( yes, can put a lock on the SIM but not a common practice. )
All that said it seems rather pre-mature. Apple eSIM support list in the USA doesn't have many MVNO.
An eSIM is a digital SIM that allows you to activate a mobile data plan from your network provider without having to use a physical nano-SIM. Find out which wireless carriers in your country or region offer cellular plans on an eSIM, either activated by eSIM Carrier Activation, eSIM Quick...
support.apple.com
Most of the super discount / low cost carriers aren't on the list. Those folks have zero relationship with the Apple store so perhaps makes sense there. But elsewhere, it actually helps with "vendor lock-in" for the major carriers if they are the only ones offering it. ( e.g. quit expensive major to save money ... ooops phone not compatible with that network so can't go.)