Well it's pretty unusual to write a Java program that accidentally parses, compiles and runs a given string as Java code instead of just treating it as data.

Shells are designed primarily as human interfaces. They try quite hard to execute data they receive, because when used interactively that is what you want. Passing around data that you don't want to be executed involves a lot of careful escaping because everything is done in-band. That's why the history of shell scripting contains countless examples of people accidentally executing file names, abuse of control characters and things like that.