Yes, this seems quite common. Jim Steranko was a classic example: here's an article about his early clashes with Stan Lee and how he got fired for refusing to change a beautiful work of art.

Steve Rude is another example. One of the best artists out there, yet he is sometimes reduced to begging for donations (for health or legal reasons) because he can't get the work he needs. Then there's Herb Trimpe: not the best artist in the world, but the best artist for certain stories: some of his Hulk pages are unforgettables. But he finally had to leave comics and become a school teacher IIRC. Even The King had to leave comics because nobody valued his work: the only place he got any respect (and a decent pension) was in animation, and there he was just one more artist among many. Comics can be brutal.

I think another reason is that some of the best artists put so much time into their work that they inevitably miss deadlines. Again, Steranko was famous for this: he was paid the basic, small page rate, yet spend hours or days on giving Marvel far more than they paid for. But all Marvel saw was a guy who could not meet deadlines. Now a good editor would say "this guy produces beautiful work, and we can sell it as reprints again and again: but he can only do X pages a month. So I'll find somebody else to do a backup strip, or fill in backgrounds, or write a sub plot that intertwines with the main story so we can use the sub plot issues at short notice without messing up the look of the main story." But instead, editors say "this guy is making me work: that's unacceptable."

Speaking as a former magazine editor: thank you.

I guess speed ( or lack of) is a factor but Adam Hughes certainly sells comics based on his covers alone. Why isn't he hired to do a one shot or graphic novel with a flexible release date? I'm thinking that maybe the artists of today are less expensive. You can put any artist on Spider-man and pay him chump change and still sell the book.

There are quality editors that are more than just editors (particularly those that are writers/artists themselves) but there are also editors that are little more than petty middle-men that seemingly only exist to stifle creativity and push their own agenda. When I spoke out against "glorified proof-readers" I'm mainly thinking about a lot of Marvel and DC editors that I've witnessed first hand screwing up series with their meddling.

That said, I'm not a fan of editors having much say in the creative side of things. Outside of checking continuity errors, and yes, making sure the product looks nice, why not do it yourself if you're so much better than the talent hired to do the job? (Rhetorical question not aimed at anyone specifically.) I guess Marvel tried that once to mixed results.

I've always liked his work and think he has a very unique style that's a breath of fresh air. That said, he's been teamed with writers the past 15 or so years that I simply don't like. The last thing I really liked was his Thor run with Dan Jurgans.

I think you bring up a good point. Some creators are simply too strong-willed, to different and too independent to work in the Marvel and DC systems. I would have rather read a Batman run by Darwyn Cooke than just about any other artist, I love that style, but a big chunk of the modern fan-base have been indoctrinated to believe that cartoony = less serious. I don't get it and think its ignorant but that sadly seems to be the case. 

As far as Steve Rude goes, I love the guys art and think he's brilliant, but when John Byrne says you're difficult to work with...yeah.

Or your Vince Collettas, who work fast and get prostitutes for their higher-ups.

Who cares if their work is actually any good? Not Martin Goodman, apparently