You mean in recent times? It's probably because the atmosphere at the company is so fickle that they believe "Power Man" refers to a cheesy, Blaxploitation stereotype that would get laughed at by the hip readers of today.

Of course, then they turn him into a gang-banger type named Cage, because that's not a stereotype at all. That's REALITY, yo.

Here are some Thor covers from the '70s..

It is interesting to see Kirby revisit Thor inked by Sinnott not Colletta

Many of those Invaders covers look like John Romita layouts.

As for speculation about what Kirby might have done with Iron Man in 70's, it's impossible to predict where he might have gone, I think. Had we tried to guess where he would have taken Cap after his long hiatus from the character, I doubt many of us would have correctly predicted the appearance of Donna Maria, the Night People, Mister Buddha, and Arnim Zola, the Bio-Fanatic.  Kirby's imagination took him and the reader to new, off-the-chart destinations almost every time.

Still, if I had to guess, I'd say: Tony would invent a space/time continuum capsule that could be swallowed to take him anywhere in the universe.  On a far distant world, he would meet a race of techno-savant cave-people who skipped fire and simple tools and created the transistor first thing out of the gate.  He'd save them from a race of dragons dressed as pirates, and find himself in the midst of a war between two men who have fought since the dawn of the last universe before this one.  He diffuses the anti-matter universe missile created by the angry, red giant "Zerk'Brr" before it can strike the calmer, more methodical Blue Giant "Nal'Ration."  The shell casing cracks to reveal the anti-universe itself made manifest as a beautiful young woman who transports Tony back to Earth to experience the wonders his charming little planet may offer.  Their romance is odd and short-lived and she leaves him for a destitute sidewalk artist who "truly understands the art of creation" in a way regimented, aggressive Tony cannot.  Along the way, they are attacked by a Nightmare Carnival, an army of technologically hi-jacked armored helmets, and Tony's own living room furniture.  Next issue: "Harken Unto the Call of the Lord!" as the Unicorn falls for a virginal princess on the wrong side of the Iron Curtain.

And I would still enjoy every weird issue of that run today...

Just a guess, though.

I never dug Colletta on Kirby's pencils. Makes it hard to enjoy the THOR ESSENTIALS in a way. I don't know what it is.

You know, what I dig about Kirby is he didn't settle for doing Kirby-like stuff. He didn't just do the Thing vs the Hulk for the fifth or sixth time (as much as I wish he had). He was interesting in other things, other causes. Even in the early 80s, still doing wild stuff like this, with Neal Adams on ish 1 and Alfredo Alcala on the others:

I only have one ish of this. I need to get the others.

One of my all-time favorite characters, his first cover. I'm convinced that X-51 would have ended up in IRON MAN had Kirby taken the title. I'd love to see how Tony might help Aaron Stack, while coming into direct conflict himself with the Corporation.

Love Mike Royer. He was Kirby's primary 70s inker at Marvel when I was going nuts over Kirby. He was on almost everything Kirby was doing, even at DC.

So did Royer follow Kirby to Marvel? Or was it just coincidence?

I'm really coming round to the power and depth of Kirby's artwork.  The only real exposure I had had to it previously was a collection of the first Avengers issues when I was a kid.  It was so far removed in style from what I was seeing in the (contemporary) late 80's and late 70's issues that I didn't really know what to make of it.  It seemed a little haphazard and naive at the time, although it seems far from that now.

It's weird how tastes and perceptions change over time, isn't it?