[pron]

1. Because the Java ecosystem usually gives you an API to everything: you can configure things to work exactly as you want. Everything is programmable and easily hackable.

2. Because everything is standardized, which is a lot easier than stitching together lots of pieces, each has to be deployed upgraded, configured, monitored and managed differently.

3. Because some Java libraries are used to do very sensitive stuff (performance wise, or correctness wise, or security wise), Java libraries, on average, tend to be of very high quality, at least relative to almost everything else (well, except maybe the Java browser plugin, but we're talking server-side here).

4. With Capsule there is no need to use a custom class loader, it's not any clunkier than Docker, and it's cross platform. It's just a cross-platform Java executable, which is stateless and requires no installation.