I was careful with my wording: 'direct illumination' - point xenon/LED directional flash at target, shoot, enjoy off-axis vignetting, severe distance limitations, extreme inverse square contrast effect, & sharp nearly-incident shadows. Reflectors ('umbrellas'), big diffusers, aiming the flash at the ceiling, all the hardware that the places you mentioned sell, are aimed at avoiding these effects while still controlling the light quality.

Amateur photographers don't know this. They use on-camera flash because their cameras force them to use flash to get a reasonable signal to noise ratio. For them (who will never even attempt to use specialized flash diffusers/reflectors), the best option for dynamic indoor & evening scenes is a bigger sensor camera, or if they want to get really fancy, aiming a speed flash at the ceiling.

Much of the lighting I do is very much direct lighting; softboxen and other play-it-safe modifiers have their place, but you couldn't emulate, say, Karsh's style with them. And the inverse-square law is your friend, not your enemy. Light is merely a tool to get the shadows in the right places.

We photograph about 20-30 weddings per year, and I can vouch for the control aspect. The color of light matters. A lot. Being able to consistently be at 5000K (the color temperature of most studio strobes) makes editing incredibly easier and quicker. Color casts from using primarily or exclusively ambient lighting can be hard to correct for and even virtually impossible in mixed lighting situations.

I was thinking more about the direction and size of the light source, actually (with contrast coming in third). I can always throw on a cut of CTS or CTO to get a near-match to the predominant ambient, and that, too, gives me a known colour temperature so RAW processor presets (or batch applications of adjustments or stored camera profiles if I'm using, say, a Color Checker Passport) can work just fine. The flash makes the diffeerence between taking your subjects to where the light is "good" and making good light happen where your subject happens to be. (Completely killing ambient means losing the context, which may be a good thing or a bad thing.)

A more sensitive and efficient sensor may make portable continuous light sources more practical in the field (modulo photon shot noise — no sensor can make light a less probabalistic phenomenon), but it doesn't eliminate the need to make good pictures under sometimes unfavourable circumstances. And unlike the stereotypical landscape photographer, an event photographer can't just pack it up and come back later when the light is better.