Someone once asked...
Someone answered with kindness...
You are taking the choice away from them. Someone you find attractive might find you attractive too, they might not. Or they might not want to pursue anything. But whatever the case, if you don't ask them out, you're making the decision that you don't want whatever might come next. By asking someone out, you are not imposing your feelings on them, you're giving them a choice with what to do with that information. Yes, it's vulnerable for you, but it is not an imposition.