| I remembered that there's no benefit to
| clearing (or cleaning) browser cache, so that can't be it, either.
|

I don't know what basis you have for saying that.
Maybe you meant benefit for the browser?
On Win9x and XP I've found that one of the worst
causes of a slow system is a very big IE cache. I
don't know why. It seems to be some kind of effect
of the generally problematic IE/Explorer tie-in. (I
don't know about Vista/7, as I don't know many people
using it and know even less people who use IE these
days.)

Additionally, cache and history can be used as
tracking devices, though that's probably not a big
issue.

Another point worth noting is that cache is, for
the most part, an outdated concept. Many sites
now assemble a webpage as it's called, changing
content, ads, etc in accord with information from
cookies and script. Static pages are becoming less
common. Even in the case of static pages, the need
to cache them is long gone. Likewise with pre-fetching.
They're both privacy risks, both take up space and
both are irrelevant on a highspeed connection.

I set my Pale Moon/FF cache limit to zero and
have done for years.