Most microwaves open the other way around – right-to-left. This design may seem counterintuitive at first, but it has a very simple reason behind it. Chances are, when you open a microwave, you have a plate of food or a cup full of a beverage in your other hand.
As most people are right-handed, you open the microwave door with your left hand and then place whatever you are holding in your right hand in the microwave.
Thus, the entire process of placing food in the microwave and taking it out can be completed at the same time.