That's not the point. Here is gmaxwell's opinion on this and I consider him more competent and credible than most: https://bitcointalk.org/index.php?topic=5324030.msg56590276#msg56590276.

I've had little experience with JS, specifically with regards to its security so I can't comment too much. I'll rather something that interfaces directly with the entropy source than to have it ask the browser for any entropy and risk the browser potentially not implementing it correctly.