One uses the packages that are available in the repositories of the distro they're using because they are compiled specifically for the particular distro. Since the software and its compilers are constantly advancing, an application that will work on one distro, may not work on another distro. It's not that the dependencies can't be resolved, but there may be different versions of the dependencies that may cause problems. When a new version of an application comes out in Fedora, and if that new version uses a different version of the compiler, I see that the whole list of dependencies has to be recompiled with the new compiler in order for it to work properly.
So, if you try to use an application that was built for one distro, a distro that say is more stable than the distro you are trying to install it to, then, the libraries and other dependencies are of different versions, and will cause errors. It's not that noone wants to solve the errors, it's that the errors wouldn't be there if you use the correct versions of the programs.
Many Ubuntu applications won't run in pure Debian because they are modified to run with Ubuntu, and these both use .deb files. How do you expect a program to run in Fedora (an .rpm distro) that was built for Debian or Ubuntu, if Debian and Ubuntu aren't compatible? How do you expect a program built for Fedora to run in Ubuntu if they have different versions of libraries?
Distro Package Managers were built to solve dependency errors, but, you have to use the packages that come with your distros repositories, or else you will have many dependency problems.