99 out of 100 of the unattached ladies Darcy meets in society would have been very receptive to a show of interest from him. Think Caroline Bingley and multipy her - that's what Darcy has been used to, without having to try to make himself agreeable. He probably knows that his wealth and consequence would produce the same result if he was a foot shorter, seriously overweight and suffered from severe acne and halitosis, so it is not a matter of personal vanity. He just does not realise that Elizabeth is not like most of the women he knows.