I did some thinking and realized that there really is no need for Google to rush to create a Firefox toolbar. The people who crave one are the same people who use the Googlebar, or know of it, and other great Firefox extensions. Also, developing addons for IE takes significantly more work than for Firefox so it would make sense that more resources are put towards coming out with the IE toolbar.

Read all that and more at http://shiwej.com/archives/2005/02/18/why-google-develop-ie-toolbar/