You'd be surprised how many Dutch people are absolutely terrible at English. Not to mention that young children (like my nephews, age 7 and 8) don't understand English at all. Even though they did play FR/LG and D/P in English. It's not so much a necessity as just convient. (I remember learning some English from Pokémon Red as a 5 year-old though )
I'd offer to help you translate the Dutch version, but I am waaay too busy. Good luck though! (And I'd offer to help translate Japanese to English, but apart from above reason, I don't understand Japanese at all, sadly).
Anyways, just posted to say thank you to all the hardworking translators and I'm keeping my eye on this thread