Well, as an example, just last week I was working on a machine that was acting weird (not a crash, but unresponsive tools in GUI) in Adobe Premiere on a new iMac. Digging though the error logs showed a path to a cache file in the user Library. Deleting that file solved the issue, and Premiere then behaved normally.
Adobe InDeign used to be notorious for corrupting/damaging cache files that would cause it to crash every time you launched it, and the only fix was to to delete the offending cache files. To be fair, this seems to been resolved in the last year or so....but it used to be a common problem. It was so common that Adobe built a
keyboard shortcut to automatically delete preference and cache files during launch. There are similar methods for other applications such as Dreamweaver, and so on.
So while I agree one should not be deleting cache files routinely as some sort of preventative maintenance or to simply save space, telling folks to
never do it seems like incorrect—or at least highly situational—advice.