as far as I know about human nature, everyone wants to get the maximum profit. and now days in the world economy, both the currency of the euro and the dollar has a lot of power and most of the volatile currency in the market. so this has great value in the market so everyone wants to deal with it and get these two currencies and its new Trader like EUR / USD and also start trading my EUR / USD. I think when new traders open a demo account, they follow the EUR / USD pair because the pair is moving every day 100 - 150 or more pips they got a good profit so on the live account next time they also choose this pair. This couple is profitable so that all new traders and professional traders like this couple.