As with most things, form trumps substance when you're selling websites to a local business. They want to have a sexier website than their competitors. Their competitors all have sites with big Flash intros and cool animations and stuff. This is what your layperson cares about when viewing your portfolio; they don't care about functionality across platforms, they don't care about accessibility or immediacy of pertine…
I'm sure this isn't an original idea but web development firms should offer a subscription package to owners. This subscription would assist them in monitoring the performance of their total web presence (not just the website which is becoming less relevant these days) and assisting them in improving it. It could certainly prove a point of difference in a saturated market especially if you got a great case study or two behind you to present to customers.
The difficulty is that site developers are just programmers and designers and not salesmen and marketers so they either don't understand or care about what I just talked about or don't know how to sell it to the business owners.