Upgrading Drupal when modules are not updated

Forgive me if this is not the correct place for this post. I struggled with where to post this question.

I have been working with Drupal off an on now for a few months. Going back and forth between Wordpress and Drupal. I like features in both and I may eventually use both together if I can get them to synch up.

I prefer Drupal because it seems to have more features and more of what I am looking for. My concern is this:

Why do the modules have to be updated to match the core each time a new core is released. I am not real familiar with the code base, but I would think that if a module is built to have it's own tables, then most if not all modules should work with a new release. Even modules that may reference core tables as long as the release does not change table names and field names, but may add new columns as needed to support new features. I suspect that modules may be using queries with Select * which may be causing some problems. Can anyone shed some light on this?

I ask this because I would like to build a new site using the new core, but most of the popular modules are not ready for 6.x yet. So, I think I will implement a 5.7 solution with all required modules and upgrade later.

I just wanted to see what the issues were as to why the modules have to be updated for each core.

Thanks.

Scott