No rule about it. ... it's not uncommon practice either.
Often enough a draw will put both of us through a group... whereas a decisive score will knock one of us out. Generally it's not worth the risk.
That said, I often meet friends in tournaments, where I'd rather just draw my way through and let someone else 'deal with them' :P.
Is that possible? I've noticed that in some tournaments I'm in people have agreed to draws before the opening phase has ended. This let both parties advance in one. Not sure what the motivation was in the other. I am not opposed to players agreeing to a draw after an attempt to win has not been fruitful but in these games no attempt to win was ever made by either side. Seems of questionable ethics to me but maybe that is wrong since there is no rule against it.