1. Most of the time ./configure won't properly support --host isn't because someone wrote their own thing, but because it's Autoconf.
2. --host is only for compilers and compiler-like tools, or programs which build their own compiler or code generation tools for their own build purposes, which have to run on the build machine rather than the target (or in some cases both). Most programs don't need any indications related to cross compiling because their build systems only build for the target. If a program that needs to build for the build machine has its own conventions for specifying the build machine and target machine toolchains, and those conventions work, that is laudable. Deviating from the conventions dictated by a pile of crap that we should stop using isn't the same thing as "does not work".