Google, Bing and the other toolbars are used to gather clickstream data... sent back to search engines to improve search results and rankings.

Many free applications bundle toolbars and other crapware as it's a revenue source, google and microsoft are willing to pay to get the clickstream data.

Some people actually like the Google and MS toolbars and always install them, I don't personally.

As long as there's an option to untick it during installation and if you do install it you can cleanly uninstall it I don't see the issue.

The real issue is spyware bundled with free programs where there is no option to not install it and/or it doesn't cleanly uninstall... Bing and Google toolbars don't fit that MO.