[nub]

Owing to its unpopularity, or to which its unpopularity owes, Apple has only supported dual SIM for a few generations.

> Curiosity: what are the use cases for two SIMs from the same country?

I have one line on Verizon and one on T-Mobile for better coverage, robustness to congestion.

iOS 13 has a "cellular data switching" feature for dual SIM that automatically chooses networks based on availability.

Data from one network even provides "WiFi calling" capability for the other line.

[signal11]

> I have one line on Verizon and one on T-Mobile for better coverage, robustness to congestion.

For cost & complexity reasons, this is a very niche need.

[jsjohnst]

Complexity is virtually zero. The most non-technical of person could set it up. Cost however is a valid point, but like OP I rationalize the cost.