Where do you think Google gets most of its revenues? They got a big chunk from advertisements. This means there is money in Google. Thus, being on the top rank can lead to generating more money towards your business, too.
Research shows that a website found on the top page of Google generates more sales compared to the ones found on the 10th page and so on. If this is the case, no wonder web owners are finding all the means to be on the number one spot. This means, more targeted visitors are coming your way. Not only that, conversion rate is much higher compared to random traffic that you most likely had before your site got optimised.
Bottom line, SEO is not a gimmick! It is for real. When proper optimising techniques have been implemented, an SEO campaign can lead towards a higher conversion rate of the traffic. Plus, there are more sales coming in. Who would not want that kind of effect? The only challenge here is for you to hire the right SEO service provider who is an expert and not a self-proclaimed one. You want to go for one who has managed several campaigns and have results to prove.