...because they're going to try to SELL you the version that does at some point in the future.
Also, MONTHLY updates aren't enough. I smell "public Beta testing program" here...and I would be VERY, VERY cautious when installing it.
That's said on the assumption that anyone WOULD install it.
Microsoft offers free anti-virus program
Security software will also sniff out 'spyware'
http://www.msnbc.msn.com/id/6794154/WASHINGTON - Microsoft Corp., whose popular Windows software is a frequent target for Internet viruses, is offering a free security program to remove the most dangerous infections from computers. The program, with monthly updates, is a step toward plans by Microsoft to sell full-blown antivirus software later this year.
Also being offered is a free program to remove "spyware," a category of irritating programs that secretly monitor the activities of Internet users and can cause sluggish computer performance or popup ads.
Microsoft said the virus-removal program will not prevent computer infections and was never intended to replace the need for traditional antivirus software, such as flagship products from McAfee Inc. or Symantec Corp.
But a senior Microsoft executive confirmed the company's plans to sell its own antivirus software, which would compete against programs from McAfee, Symantec and others. Microsoft purchased a Romanian antivirus firm, GeCAD Software Srl., for an undisclosed amount in 2003. Industry rivals expect Microsoft's formal entry into the market as early as the spring. "We will have a standalone antivirus product that is one of the things you can buy from Microsoft, but we're not announcing anything today," said Rich Kaplan, vice president for Microsoft's security business and technology unit.