They could just use the heavier cord only, it would be fine. I don't think anyone in usage would even notice the difference.
We have 1 plug for a whole continent. Nema 5-15 is most likely the most common electrical plug on earth, it is not the issue. Very few items ever run near 15A even at 110V. As most items got more efficient (tvs, computers, etc) most items barely use an amp. So there is no reason to change things. When we have big stuff, we have other plugs, such as those for ovens and such, these are far more powerful than the plugs you guys have. We have plugs that do 60A at 240V. Many 110V circuits in our homes are 20A circuits. Code requires them in various places (bathrooms, kitchens). Custom built homes and such often have all their outlets as 20A. Of course almost no appliance comes with a 20A plug, but that's ok, it means the circuit can handle more items at once.
For the big tools like the OF2200, Festool could have given it a 20A plug. They also could have gone to 240V, we have 15 and 20 plugs for that too. They just aren't required by Code, so builders don't install them. But folks wire them up in their shops and garages regularly to run tools that run on 240V.
240VAC is nice, but it's not without issues. The main thing is safety. US is 120VAC to ground/neutral, and due to split phase power, even when something is 240V, the potential is still 120V to ground, only directly across the pins is 240V, so you would have to short it and not ground out at the same time. So there is a big safety benefit. The trade off for some higher amps isn't much and few items push this limit. We wire with heavy gauge wiring, and high temp limits. Trying to use the smallest gauge wire is not a priority. A zap of 120V isn't pleasant, but you manage. A 240V zap is not good at all. As has come up in various threads here. We are not amps limited in this country. The smallest legal service is 100A, standard is 200A, many homes have 400A services to them. We don't have to concern ourselves with trying to use as few amps as possible for fear of running out. I'm not against the 240V stuff, but the focus on safety in this country makes elimination of 110V power very unlikely.
The lighter gauge cord is just something Festool never had to do.