Couldn't help it.
The reason is that viruses are plentiful and always changing or mutating if you will. This is difficult to combat with one software package.
This makes for a moving target that can only be hit as an after thought, sort of like a vaccine developed for a real virus after it has been around for a while.
There are several layers to security. Different attacks need to be filtered out at different layers. Each scan takes time and adds to the suckiness of the virus fighting software. Especially given that most stuff is not virus related.
- Point of entry.
- Processing Execution
- Point of exit
I wish I had some more time to go into it now, but sadly I have too much to do right now. Just compare it to your own home security and look for the ways to break through it and you'll get some more insight that way. Think about how much easier it is to bypass security efforts such as strong doors by going through a whole in the wall, etc.
The bright side is that the more experience that I gain, the better the chances are that my original design had fewer errors in it, and the better its chances of turing out closer to the vision.
Anyway, I'm just trying to add some clarity and bring in a human factor to the discussion. There are feelings and issues that almost always boil down to less than a handful of people's motives and desires that produce a given result.
By the way, I'm a computer professional and not some idiot that barely knows how to use the internet. I've written webservers and email servers and basically done more technical crap than 99 percent of the people on this forum.
So, feel free to have whatever opinions that you want about this subject and my post, but also be conscience that I'm not speaking from a mal-informed perspective.