All browsers should ignore any tags between the HTML comments. So, what you posted should just be one big comment, and ignored by any well-behaved browsers, including the ones that support CSS. Probably this is what you meant (at least it has some chance of working):
<style ... >
(some style definition)
I think you are confused. There were known problems with some older browsers showing things between script tags, so the advice was to use this:
<script ... >
(all the script stuff)
which makes all the code an HTML comment, and prevents literal characters from screwing up the real HTML.
Since there is nothing in the style structure that looks like HTML, it should never have been a problem. I think that someone thought it was a good idea and nobody ever questioned it.