Why is the antivirus (paid) not free?

Recently wer cousins visited they have no idea about the DSL 100000 and how quickly the Trojan/Virus infect your PC.

I had a paid version of virus namely Antivir this did not Detect the **** of the virus total data lost 30GB only able to recover some windows files. why are the antivirus (paid) are not free when they are not stated to work as it in the site?

mind you;I have been careful with my PC all of my LifeTime.

Why is the antivirus (paid) not free?windows

Antivirus programs generally only detect items for which they have signatures, and do not detect all malware across the board. To truly be careful with your PC, you need to have a good firewall, spyware protection, virus protection, and preferably at least one intrusion detection/prevention application. Finally, you need some reliable backup method that you use on a regular basis.

If you need freeware security applications, you can choose from the following:

firewall: (listed in order of preference)

Comodo (http://www.comodo.com ), or

PC Tools (http://www.pctools.com/firewall )

Comodo recently released version 3.0 of its firewall, which adds an intrusion prevention component that's very effective, though it does take time for it to learn your system, and requires some ongoing attention by the user to make sure programs don't get improperly blocked. Comodo is one of the strongest firewalls available, freeware or commercial, according to the independent testing site matousec.com.