The use of a good quality 2 cycle oil at 50/1 obviates the use of additives for two cycle fuel.
One could make the same argument for the operation of a newer gas powered vehicle, the fuel management and engineering eliminate the use of additives.
Where a product like Seafoam (or the homebrew) really shines is with storage situations, where the additive acts like an anti-oxidant to remaining fuel in the supply. Seafoam can also induce an engine with fuel issues to become operable but that is a rare occurrence.
Gasoline with additive alcohol blend has to be different for different regions of the US. There is no other reason why anecdotal success is related by some and others, like myself, have no issues with 10% blended gas. FWIW, I maintained and operated a fleet of small gasoline engines for 6 years, all on 10% blended gas. Beyond that, we had 30 or so 2 cycle engines, also using 10% blend. The 2 cycle fuel was mixed in 55 gallon drums using a 50:1 oil mix.