Samsung caters to the needs of almost every segment. In India they have hugely popular dual SIM (It's a big deal in India) Android phones. I'm sure there will never be a dual SIM iPhone ever. Samsung phones are available even in remote villages , but iPhones are only available in cities.
Apple will have to improve their distribution and variety to appeal to new users. So , this trend will only accelerate
In case of my wife, she has a private phone number only for friends & family and another one strictly official. There are many uses ,
* If she leaves her job she can give the SIM back to the company and won't get anymore calls on that
* Separate billing. Company pays for official calls only
* Switch On/off one SIM or other when required
The other use is for bargain hunters. There are so many operators to choose from. The ones with wider coverage are expensive and the others are dirt cheap . So the cheaper one is usually used for making outgoing calls when the signal strength is good. The expensive ones are used for incoming calls (which is free in India. Here calling party pays) or even for outgoing calls when the other one has poor signal.
Carrying 2 phones is expensive/inconvenient . So most of the feature phones come with 2 SIM slots in India. Smartphones are now catching up
