Well, that is the same as asking "what is the point in Firefox allowing support for addons? Every time I update to a new version of Firefox, half of my addons stop working!". Are you suggesting that Firefox also stop supporting addons? :-)
This issue is true of all applications that support addons. The more sophisticated and complex the addon is, and the more it ties itself into the way an application works, the less likely it will work in the next release of that application.
I think the way new versions of Firefox disable addons that have not been updated is a good idea. It forces old addons to be updated and if they are not, they stop being used and other addons take their place. This ensures continued addon development and prevents users from becoming dependent on old addons that never get updated.
