In version 1.2.9, which is the latest, the two attributes you mentioned are deprecated. Just eliminate them, and the form will still work fine. The reason these attributes were deprecated is that they're already defined in the struts-config.xml file, and are therefore unnecessary.
I can't really say which version the majority of developers are using. I'm sure, though, that many are sticking with the older releases because of conservative adoption policies taken by their companies. Another factor is tooling. For example, even the latest version of IBM's Rational Application Developer IDE is tooled for Struts Version 1.1.
In one sense, this says something about the fact that Struts is a very stable product. The later releases aren't hugely different from 1.1, and unless one needs to use one of the new features, there isn't really a lot of motivation to upgrade.