I think Soak in concept would be useful on certain defensive/support Pokemon because, as noted, depriving attackers of STAB can dampen their output a decent bit.
The issue is that there are very few OU viable Pokemon of that sort that have access to the move (the only 2 OU viability listings with it in their movepool being Pelipper and Tapu Fini, both of whom have moveslots at a premium). Even as a very specific Lure to generate momentum, the idea is incredibly restrictive on OU teambuilding for what will, in practical terms, at most result in one free turn to double switch or set up something like an entry hazard, since the effect disappears on switching out. While that would be a helpful gain in many teams, the cost to achieve it in this specific instance seems too steep on the teambuilder.
The issue is that there are very few OU viable Pokemon of that sort that have access to the move (the only 2 OU viability listings with it in their movepool being Pelipper and Tapu Fini, both of whom have moveslots at a premium). Even as a very specific Lure to generate momentum, the idea is incredibly restrictive on OU teambuilding for what will, in practical terms, at most result in one free turn to double switch or set up something like an entry hazard, since the effect disappears on switching out. While that would be a helpful gain in many teams, the cost to achieve it in this specific instance seems too steep on the teambuilder.