Try/Catch only affects the throwing of exceptions, not PHP Errors.  We can't assume that Memcache, APC, XCache, Database Cache, and File Caching will throw exceptions and not generate errors when there is a failure in cleaning the cache.  As the current cache engine modules are not designed to handle common configuration problems, they will frequently generate errors instead of exceptions.  For example, if the XCache extension is installed and Joomla tries to use it by default[which happens when the file system permissions are set not to be writable]] BUT the USER did not plan on using XCache so they never configured it's php.ini settings for xcache.admin.pass - http://xcache.lighttpd.net/wiki/XcacheIni

Both xcache.clear_cache and xcache.get_list are Administrator functions
http://xcache.lighttpd.net/wiki/XcacheApi

So Joomla! will call xcache.get_list when cleaning the cache - without the password set this generates a low level PHP error and aborts processing.

Error suppression is the correct solution for this particular case - this case being that there is no interest in actually implementing and fixing caching bugs in Joomla!   I submitted the fix for this XCache issue over half a year ago - it is reasonable to assume that because of the nature of these bugs they will not be fixed.  XCache is not the only caching mechanism with this sort of error - I just am not bothering to submit simply 3 line code fixes on all the cache methods - it's a waste of my time to setup the unit tests and work out all the parameters if no one will test them]

I'd rather have something that works and 'feels wrong' then have something broken and never fixed because only one person is willing to spend the time on fixing it.