I'm not suggesting that's how you do business (by word of mouth), I'm saying that's what I'm generally willing to do in exchange for good work. I guess as I think of it I have done an online review for either exceptional or exceptionally shitty service, but not often.
There are definitely a portion of people who rely on google and other online reviews to find their contractors and other services. I don't know what data there is to show exactly how successful it is using google or others to advertise yourself though. Like how many reviews does one need, how many good vs bad reviews do you need, if you have say 20 reviews how many of those are the average customer going to read? Can only guess at this, but I suspect that google is a better form of advertisement when you can get your business to appear in the first page of results, and the higher on the page the better. Only reason for this is the average person is not going to go through all those results & reviews, maybe look at the top 3-5 results and choose from among them.
I'd also consider that if you and your competitors are currently doing an even amount of business while you have far fewer reviews than them, then is the number of reviews relevant? What are you doing that's giving you an even amount of business with less online presence? Somehow you're compensating, how do you do that more?
Keep in mind too that there are marketing groups and motivated individuals who fabricate all those reviews. Paid for reviews, or their website features testimonials from fictitious people, etc. How would anyone know?
Fully understand your frustration and again, you're not the only one who has expressed similar on here.