Reasons are

1. This is a generated directory, none should touch nor version control
2. even mvnw.cmd mvnw should not be changed, let dev know to use the command ./mvnw -N wrapper:wrapper -Dmaven=3.8.7 to upgrade maven from command line
3. I love developers using a different versions of java, mvn etc to report compliance issues early on, rather than enforcing just xyz version of java etc..
4. If strictly required java version and mvn version should be captured in pom.xml