The players are paid by the sponsors. The money they win is supplied by the sponsors. The sponsors want the players to deal with the media and the media deals in English.

If the players don't want to speak English, they can find a tour that exists where the primary language is their own.

If no LPGA players speak English, do you really think the LPGA will get sponsors?

I am pretty sure NIKE asks all of its athletes to be able to speak some English for marketing reasons.

The LPGA is asking all of its golfers to be able to speak some English for marketing reasons.