Plugging directly into 120-250v approximately 15 amp source depending on your country, directly would be ridiculous. You would have to build it big enough to hold a power supply, have a large power port and shield the hell out of it. It would also be capable of killing you instantly in case of a short. What they did is fine, it can be built exactly the same no matter where its used, is small and lightweight . Plus has the added benefit of not killing you, unless you walk into traffic while using it. Powering it is not difficult.
There are plenty of power strips out the with usb power ports. I paid about $29 for mine at amazon. A USB-C to standard USB adapter and a long enough cable to reach the power strip and the strip can power other things on stage too. That's what I use to control my mixer. It will charge an iPad albeit slowly, but keeping it powered it works perfectly.