Earlier quoted context omitted.
Many do it to get practice speaking English, which makes it mostly a win-win as players get to have controllers who take the game seriously and the controllers get to hone their language skills. It's only a problem if someone's accent is very heavy or they haven't achieved enough English skills yet to be able to communicate the basics of ATC but neither happens very often.
Sometimes I can tell where my ESL coworkers learned English based on phrasing and idioms. It would be interesting to come across someone who honed English skills with such a domain-specific application.
I worked with a mainframe operator that learned English from I love Lucy. It was interesting..
He honned in the Ricky pretty well I thought it was a gag but no its how he learned.