Yes, we officially stopped supporting ASP in new extensions a couple of years ago now. The audience was dwindling and frankly the technology is antiquated and inferior to PHP. We found ourselves having to leave out really cool features since they weren't possible in ASP, it doubled our engineering and QA time, and at the end of the day ASP is a dying technology and we had to jump off that ship before it sank.
If you want to maintain ASP and PHP sites instead of always installing and uninstalling you can maintain two Configuration folders. One with all of your old ASP extensions and one with all of the new PHP ones. Then you can simply close dreamweaver and swap out Configuration folders to quickly uninstall and reinstall all of your extensions at once and without having to wait for the extension manager to do it.