Yes it's true, you need to optimise every page on your site to get the maximum bang for your bucks. However while this entails a fair bit of work it does give the opportunity to create landing pages for different keywords or phrases, and in the escort industry this gives us some useful tricks.
Firstly, the keywords we usually want to target tend to overlap each other, for example if your optimising for say "escort in some town" and "some town independent escorts" pretty soon your going to run into the problem of keyword stuffing by overusing the word escorts. This is a problem, both may be good phrases for your needs, but trying to use both on a page could actually have a negative effect.
Simply put, a landing page is a page that you'd like your site's visitors to 'land' on, and a page you'd like to rank in search results for a given term. You can hardly have one and the same page optimised for all your keywords, so you'll need to look through your list of keywords carefully and decide which page is the best fit for each word or phrase. That page's content should be useful and engaging and, most importantly, relevant to the term, ensuring that the searcher finds exactly what they're looking for on your landing page, and sticks around your site rather than bounces back to the search results.
For example on "independent escort web design" is matched to the independents page, while "escort agency web design" is matched to the agencies page. Each page is structured as a viable entry point to the site, is relevant to the keywords and is still part of the larger site structure.
For say an agency, a filter page showing all blondes or escorts in a particular town provide good SEO keyword opportunities. For independents, the profile page can detail location and statistics, again providing opportunities for a landing page for example targeting "location busty escort".
Using this system you can avoid over using a particular word while still getting the keywords into the site and hopefully Googles rankings. Go to it, and remember if you would prefer some professional help, please get in touch.