So what. People care about having things work straight out of the box from day one. Sure, we have had dozens of 5v, 9v, and 12v DC/AC Adapters with the barrel plug. It makes no difference. Sure, people have 5v USB charging adapters but you have to have ones rated for 1.0 to 2.0 Amps for devices like this. Some of the USB adapters are only 500 mA and is for charging the built in battery not running the device off it or the device has to be consuming power within the 5v @ 500mAh rating.
Considering Nintendo's is deliberately under-supplying the demand and attention isn't on the lack of ac adapter. Point is, why be overly cheap by making someone have to unplug and disconnect their router or whatever so they can use that power adapter or have to go out and spend more money than it would cost Retro Games Ltd to include it due to bulk order discounts they would get by ordering 1000s. If it cost only $10 as the local best buys or whatever, it would cost these guys maybe $2.50 ordering them in high volume. Maybe, $5 at most. I can get them from Jameco for around $2.50 to $10.00 depending on what I want to supply. Keep in mind, Jameco marked up from what they paid so they have their profit margin.
Commodore 64 computers were supplied with power supplies, why not be at least authentic in that it is supplied with a power supply. We only hope they work better than Commodore's early power supplies for the C64. Lets just make sure we don't over cheapen. Provide the power supply so people aren't having to go out and buy one even though they probably have 5 of them and all of them are being used to charge their other mobile devices.