Apple wants all of its developers to use 64-bit applications. In its view this is obviously a better solution, and to push that through Apple has removed all support for 32-bit applications in Catalina. That means that countless legacy applications and previous versions of popular apps will no longer work.
What warning do you get during the installation? A nondescript dialog that pops up to say your 32-applications will not work. And if you get all the way through the installation of the OS update and find out that your key applications are 32-bit and no longer run, well, you’re out of luck.