Sometimes a website's message is bad because there's so little behind it. As Bruce MacEwen puts it, there's "no window into the strategic planning process", and a lack of true differentiators.
I think most of us recognize that good writers can make a difference; occasionally generating that 'homerun' sound bite out of nothing. Even in the examples MacEwen uses, I can sense a little wordsmithing at play with a phrase like "getting into client's heads". But the critique here is sound. Just because you write something on your website, doesn't make it true. And whether intended or not, a lack of accuracy in your website's message can be incredibly destructive.
Destructive because it creates mixed messages. What does it say to existing clients when a firm has significant history and standing in a smaller community, yet their website claims to be a national provider? Or perhaps the website claims the firm is "full-service", despite having spent decades developing a boutique status.
It happens… And when I've encountered it, I would almost always classify it as unintentional, and rarely deceptive. Firms are simply (and at times aggressively) projecting who they want to be, rather than who they currently are.
So why does this happen? The business of 'firm building' (like most businesses) has a strong element of ambition. Lawyers are often ambitious people, and if you're going to dream… dream big! The problem with dreaming big, however, is the tendency to be blind about the firm's brand — as it stands, right now. Mix in the expertise of marketers who are often gifted at embellishing, and we end up with an inaccurate message — based on a firm's future dreams, and spun to be more than originally intended.
Strategic plans help firms know who they are, what they want to be, and how to get there. Having that context as an input for the development of a website's message would be fantastic! Is your website's message better served being driven by the firm's overall strategy? In many ways, yes. But it is only an input, and there's more work to be done beyond working directly from a planning document.