There are 2 Categories of Third Party Software / Services that are baffling to me.
Why some users insist on installing and using the below software.
In no special order
Commercial VPNs
They may not be what one believes they are doing for the computer and what they actually are doing behind the scenes
https://gist.github.com/joepie91/5a9909939e6ce7d09e29
Third Party Disk Cleaners / Optimizer
Any Third Party Applications that will interfere with the normal operation of the OS, is an invitation for disaster.
Certain Applications maybe available on the Apple Apps Store - this only means the Developer is prepared to pay Apple a percentage on each sale.
What the Application may do to the computer is up to the User to check this out before purchase
To put the Third Party Disk Cleaner / Optimizer in context and the damages it may have or has already done.
This type of applications can or will Muck Up your User Account ( Home Folder ) of this machine.
It does not touch the Operating System itself unless you consider your User Account ( Home Folder ) as part of the Operating System.
The Operating System is hosed