There is no reason not to provide all the stable branches and development/bleeding edge branches for packages and let people choose what they want, except for package management practices still stuck in 20th century.
It would cause a combinatorial explosion: if you have only 10 packages with both stable and bleeding edge branches, this is already over a thousand possible combinations. That makes it harder to support, and the whole point of an LTS distribution is to have support for a somewhat longer time.
But it's all tied to time. So, for example, at any point in time there are latest stable packages that should only depend on other latest stable packages, there is no point doing other combinations, hence no combinatorial explosion. And if it doesn't work with the latest stable dependency, it will never work with it anyway and has to be linked with previous stable branch of that dependency, still the only version though and no combinatorial explosion. No matter how you look at it, time constraints possible combinations to a small number.
So use the regular releases, they are just what you want.
Indeed in ideal world that would be the perfect solution.