Spyware and other malware

I was speaking with the team this weak and once again I'm puzzled. Why is it that spyware is such an ongoing problem, and to quote some, "why do we have to load additional software simply to protect us from the inability of operating system developers to create decent software." I had to guide my mom into removing 20+ high impact nasty bits from her system. This was identified by Microsoft's Defender. Point One - To me it seems that spyware should be as simple to alleviate from our systems as viruses. Symantec, CA and McAfee along with some other niche players all do a very good job at protecting us from viruses - including from mail and web sites. There continue to be new viruses, trojans and such, and in general they respond to these fairly quickly. Much of the Spyware that I have encountered does load files onto my system, it should be rather easy to develop signatures that detect this spyware, tag it and alert when it attempts to save. If there is a financial reason for buying new elements of protection, that I can at least understand, then simply charge a fee for enabling the spyware protection, it shouldn't require different software. Point Two - There seems to be an explosion of this nasty stuff and the load that it places on the system is rather high. I am still curious as to what this software 'spies' upon, what information it collects and what is the value to the producers. Many of the warnings about this stuff warn of personal information being stolen and abused, but I for one have never read or heard of a report of this happening. All are accused to collect marketing information - what they are collecting is obviously what web sites are browsed and such which I suppose could be used by marketeers, but I don't see reputable companies looking to the likes of comet cursor for marketing data. Then again sleaze associates with sleaze and I suppose all of them simply share data amongst themselves.