The features that make Eclipse popular are; it is open-source, today’s most popular languages are supported, and will look good on your resume.
A lot of the post on this website are about open-source software. This is because being open-source is awesome and it gives us, the users, more power to direct the software developers where we need the software to be. Eclipse is open-source and because of that, it already gains a lot of merit. The community is highly active in the forums and blog posts and there is tonnes of help available online.