Not to be dismissal - but that sound anecdotal.
I think it's best startups are provided with the most tools/options based on their priorities -- including the underlying lessons this book attempts to deliver - is the right path. Then it's up to their values and priorities.
Ignoring my startup experience (as they are all security-related and therefore took it serious), I believe startups that are handling any amount of customer data should be looking at security very seriously.
Now whether or not they do take it seriously is another problem, that doesn't mean the opportunities and advice shouldn't exist.