Voltage is derived from chemistry. There is an electric pressure associated with different reactions, and a battery is a device for creating a lot of this pressure in parallel. The basic reactions tend to produce something in the area of 1.5 volts. This is normal for alkaline batteries, the sort you are used to.

The devices we power with those piles usually need more power than this. My knowledge of this is very dated at present, but it comes down to the kind of transistors in the chips. You get about 3 volts out of 2 batteries... Roughly 5 volts out of 3...