The answer is simple when you understand why it DOES work for the other 6 businesses — no two businesses are the same, nor should they be treated as such, even when they’re in the same industry.
Instead of trying to go for the hard sale using lead generation advertising, you should be running awareness campaigns; they’re much cheaper, and they increase your referrals rather than trying to get random people from the internet as your clients.
Instead of trying to make more sales, make yourself famous within your target market and the referrals will start pouring in.