Post your cards that (99% of the time) opponents quit if you use in the first round

I don't understand why Elvish Insight could make someone resign first round (actually today a guy just resigned right after I used Elvish Insight on him).
It reveal their hands, right. But first round it hardly matter. 90% first rounds are just to get close to each other, after that you discard half your hands anyway, so it can give the opponent an advantage but it's not that OP to have to quit right away.

Personally I don't use Elvish Insight the first round if I get it, unless I have others cards I don't want to discard in first turn.