There are good reasons why some SEO companies may not want to appear at the top for SEO type phrases - it depends on your target audience and your business model.
Typically the phrase 'search engine optimization' is not used by our target audience. We get most of our business from referrals and networking - most of it local to our region. It is not worth the effort and cost of getting in the top ten for these extremely competitive phrases.
The most important measures are whether their client sites are ranking well, whether they continue to rank well, and whether they deliver traffic.
We have a few customers who are happy for us to show their server log analysis to our prospective clients - that usually does the trick:)