There is no reason why you should not own dual SIM phones. There are plenty of them on the market coming from a wide variety of brands. They often feature a removable SIM tray that can be ejected with a pin. Place your two SIM cards on the slots so that you can receive calls and messages from two different numbers. One could be for personal contacts while the other is for business.
You could also use one of the slots for the expansion of your phone’s memory capacity. Manufacturers put a high premium on the built-in storage of their products. You would have to pay a great deal of money just to get a model that fit your media collection. With the extra SIM slot, you can opt for the budget-friendly model and just insert your spare microSD card to improve capacity.