My local PC repair shop say that Advanced System Care among many other "registry cleaners" "PC speed ups" "Driver updates" and such like "tools" bring in a high percentage of their work from those conned into downloading and using them. In the long run they do more harm than good. One or two of the download sites sneak them in when downloading other software, in much the same way as they push "Browser toolbars" "Quick search toolbars" etc. Quite a few of the cleaner or Update ones report finding loads of problems and asking you for £/$/€xx for another download to fix the problems.
There is often a very small print option to opt out of the download or installation, if you miss that you could find yourself with all sorts of annoying pop ups, or having our searches hi jacked by Snap Do which is almost impossible to remove - took me over half a day to get rid of it, some equate it to a virus in disguise.