tarballs are usually highly customizable. even though with 90% of them you just go ./configure && make install, some others require custom parameters or in the worst case they use different steps to buid the application.
imho as a normal user you should not have to deal with tarballs. you might be better off checking if it's in someone's repository first.
the problem with tarballs (as an install method for endusers) is that:
- if something goes wrong you quickly need to be very tech savy to fix it
- doesn't necessarily adhere to the folder structure of your disto
- not always possible to easily uninstall software again.
to your second question: yes, this process is automated with debian-source packages or rpm-source packages. but those aren't problematic and i think they can just be opened in gdebi. i am not sure you know, but a tarball is the easiest way a developer can get their code out into the world. no matter what mess they have in their project, just zip up the source and upload it--- that's the only requirment i know for a tarball: it must contain the source of some app and eventually provide a build script.
so even though its not going to work to use those tarballs directly, i think you're touching on a very important issue here: linux packaging is a mess. its a lot of work even for a single distro and it's practically impossible for a small project to maintain packages for a variety of distros.
there were (and still are) a bunch of projects that tried to unify packaging across distros, but afaik this never went anywhere really. at least nothing that is as common as an msi package for windows or a dmg on the mac.
i know this answer must be frustratring, but if i haven't missed a revolution recently than that's what we're stuck with for now.