Ubiquitous
It's available on any Unix box, so you can just ssh into the box and start working. With little configuration, you'll feel right at home.
Fast
Its performance on large file (100+ MB) is ridiculously amazing. And yes, Performance is a Feature.
Reliable
Vim is 29 year olds and actively maintained. Its predecessor, Vi, is more than 45 years old. There's also many successors, most notably is the Neovim fork with even more features and optimizations. You can safely assume that Vim is still there for 50 more years.
Text Editing Language
As you use it you begin to think in it. Vim is set up to function like a language, complete with nouns, verbs, and adverbs. Once you learn the language, you will see there's no better way to edit text. The side-effect is you'll stuck with it, no way to exit.