Earlier quoted context omitted.
Why would you need a package for Eclipse. Download it is a ZIP, extract it in the location of your choice and run it from there. (Portable app) I have been using it like that almost every day for 15 years now.
Eclipse isn't portable, somebody has to compile it for Linux, it just comes down to whether you want that done by the Eclipse Foundation or Debian people.
My theory is that it is obviously because there is a way how to run Eclipse, without any issues and without the need of an officially tested debian package, so there is not huge demand.