Considering 1,3-butadiene (below) added to bromine water (considering it as $\ce{Br2(aq)}$):
I've seen online that the products are 1,2-dibromobutene and 1,4
but what I don't understand is why wouldn't the other double bond undergo substitution again? They're on a carbon chain like normal so shouldn't they react with the bromine water too? Is something stopping it?