Well incentive is to help, it will surely bring more entropians. I guess UK/US people thinks 100% of world population speak english
On the other hand, even when i joined
PE in early 2006 there was a 'preferred language : french ' setting while account creation. It took time but it will be here soon
I don't know what is it exactly yet, but you can bet it will help in some manner to growth
EU population alongside spanish , (..german? .. chinese ?,etc) client localisation.