While that might make sense for some companies, it would be a bit backwards for Google. Android is used as a means of getting users to use their services (Google Voice, Google Maps, etc). As such, restricting app use to attract users to Android would be like restricting google.com to only run on Chrome to promote their browser.
My fear, though, is that Google consideres web apps better than 'regular' apps - this is apparent in their decision to integrate VOIP into GMail instead of releasing their Google Voice app that had been in use internally for some time:
http://techcrunch.com/2010/07/01/exclusive-video-of-unreleas...
This is unfortunate because, although web apps will do in a pinch, they really are second-class citizens on the mobile platform, unable to run as fast or have access to the system APIs that native apps get, and if Google Voice truly wants to replace my dialer I need it to work even when my data connection craps out.