1) are less verbose
2) don't require worrying about typing
3) have really easy ways to manipulate strings, iterate, etc., which are often found in interview style problems
Java and C# have many advantages over python and ruby, but I think that they put you at an inherent disadvantage for many interview style questions which often require you to solve an algorithmic or data structure type problem in a limited amount of time [1].
[1] This doesn't explain why people using Go would tend to pass at higher rates, but since the Go community is comparatively much smaller, there could be other factors at play there.