I don’t understand what the purpose of anti-virus software is or why you should have to buy it. Shouldn’t an operating system be secure and provide automatic upgrades, so you don’t need external software just to ensure your computer is secure ?

Then again in 2016, I don’t know why anybody would use anything but Ubuntu Linux on their computer. It takes care of the all upgrades itself and you never have to pay for add ons. The software is quite well developed at this point and unless you have special technical needs, there isn’t much of anything that can’t be done using.