[invalidname]

Because it's very literally decades behind Java on almost every front. It was designed for system programming whereas Java is an enterprise platform. On observability Java stands alone. Far beyond anything else (including .net). E.g. check out OpenTelemetry to get a sense of how far ahead Java is on that front. It does all of that without impacting performance in a significant way.

In terms of 3rd party tools. NPM has more packages but they are simplistic toys for the most part. Java has a fantastic number of packages to solve every niche problem you can think of. These packages are at a maturity level that no one can compete with. Hibernate is so far ahead in the ORM field that there's no point comparing it to anything else...

The same can be said for Spring, it is massive. In a bad way as well... But that mass is without competition. You need to integrate with something, there's already someone who built that and it probably works with Spring.

Then there's scale... Horizontal and vertical scaling and the set of tooling to measure that it works properly. The question isn't why don't people switch to go, the question is why does anyone use Go to begin with?

To a large part it's a combination of ignorance about Java due to the vast amount of stuff that's already out there. A hostility towards the language which is redundant since there's Kotlin, Scala, etc. or problems with Oracle which is something I actually get... I use OpenJDK but Oracle does loom. Go feels like a toy. If I were to build a system level solution I would use Rust which seems superior in every way. For high level stuff the JVM is without competition.