With low Volt electronic A/C transformer, higher voltages are to compensate for the voltage-frequency ratio output on the load side. Typical "puck" light electronic A/C transformer steps up the frequency from 50 or 60 Hertz to around 19,000 - 28,000 Hertz. Manufactures step up the voltage to 24 Volts on their more higher-end products.
Instead of using a low Volt electronic A/C transformer, there is also a low Volt direct current transformer. These do not step up the frequency because they are direct current, but certain installation cautions need to be followed. Namely, the polarity needs to match, and if any dimming of the LEDs are needed, a direct current rheostat has to be installed on the load side of the circuit. Also, I would keep in mind the voltage drop would be an issue of longer runs were to be required. For this case, a higher voltage would be sensible.
A typical LED strip from the hobby store is probably D/C. Keep in mind you cannot mix and match D/C and A/C. You have to stick with what the product is designed to use. I prefer A/C because they work with most existing rheostats and polarity is not a concern.