I can already see myself, as a tourist who buys a US SIM card to get data on vacation, having to add a SIM card swap to this ordeal to confirm debit card transaction via my EU phone number. Why, oh why...
My understanding is that the current iPhones offer both a traditional SIM card slot along with an esim, which gives you the option of two sims provided one of the carriers supports esim.
I also believe that current iPhones sold in China support two physical SIM cards and no esim.
That could have something to do with it. I've ordered from India before when I wanted a dual sim android. Local stock for that model was single sim only.
Looked at gsmarena now and indeed most models have dual-sim versions (as well as single sim). But when I look at a local store, it seems that roughly 1/2 has dual sims (that's including eSIM).