Based on 0.1" spacing, this 3-pin header spacing is a very popular way to interface sensors & accessories to your design. Ground / Voltage / Signal!
Pins are cool. They are one of those things you simply need to have a good number and assortment of. If there is one small type to have on hand, it is this 3-pin style, which is used for all sorts of interfacing. Ground/Voltage/Signal, Rx/Tx/Ground, 2-position selectors - these are all things they're good for!