The biggest issue between physical and special moves isn't the power, it's how special moves can easily be made "generic," or not tied to specific body parts/actions, where as physical moves usually are.
Tri Attack/Hyper Voice, Flamethrower, Surf, Thunderbolt, Energy Ball, Ice Beam, Aura Sphere (for lack of a better option here; it at least is a TR now), Sludge Bomb/Wave, Earth Power, Air Slash (there's an odd gap here for sure), Psychic, Bug Buzz, Power Gem, Shadow Ball, Dragon Pulse, Dark Pulse, Flash Cannon, Moonblast/Dazzling Gleam
Almost all of the "generic" "strong" special options for moves aren't tied to specific body parts or being able to perform specific actions and involve shooting/projecting energy to attack. Easily distributable and applicable. The only ones, IMO, that are "restricted" by the user are the Normal-typed options, Power Gem, and Moonblast (which at least gets a widely-distributed, only-slightly-weaker replacement for singles). Bug Buzz should be (why can Accelgor get this), and possibly Flash Cannon as well, but basically all Steel types have a metallic luster so it's a moot point.
There are exceptions on the Physical side, but they tend to be indirect contact attacks (Earthquake, Rock Slide, perhaps options like Seed Bomb and Icicle Crash as well). Ramming attacks have become more commonplace and can make for a good physical option that is easily distributed, but most of these come with a recoil penalty. Physical moves tend to have more "cost-of-use" requirements or considerations than their similarly-powered special counterparts as well. Wild Charge vs Thunderbolt has been talked about a lot here (recoil), but there's also examples like Icicle Crash vs Ice Beam (weaker AND imperfect accuracy) and Phantom Force or Poltergeist vs Shadow Ball (both stronger than the premier special Ghost move, but Phantom Force has a charge-up turn, and Poltergeist has imperfect accuracy as well as the conditional of the target needing to be holding an item).
Anyway, as a result, physical moves tend to be more specialized than their... special... counterparts, which limits their distribution and leads to a lot of good physical options being signature moves.
I also once heard someone talk about how a lot of types have a specific kind of "move design" which reflects on the effects or drawbacks of a move, but i don't feel like getting into that.