Delivering by Development rather than Sanctions
We create exception guidelines and laws in society to protect its weak, vulnerable and less empowered members, the hallmark of a civilised society. They are enacted by (hopefully) responsible individuals whose legislature, where ordinary collective morality or education fails, is used to sanction those whose actions - irrespective of ignorance or intent - jeopardise the rights of others.
In America you have ADA (Americans with Disabilities Act) and the Federal Section 508 amendement (not punitive but procurement guidelines), while we in the UK have the DDA (Disabilities Discrimination Act) through the DRC (Disabilities Rights Commission). (Other country policies and agencies.) These agencies and their rulings in law aim to protect those less fortunate, whose challenges with physical and/or cognitive impairments may alienate them from the normal course-of-life activities and transactions more empowered individuals assume as a given. It's how civilised societies should operate.
Money talks - as a positive through revenue or a negative through sanctions. The trouble is, businesses can afford to take a hit when the equation is weighted in their favour: annual web revenue from portal sites, travel, hotel, retail ecommerce, what have you, generates, say, £10 million and when a legislative sanction amounts to - what's the latest? - $20,000?, then the maths works for them.
Woolly DDA Legislation
Smaller companies are unlikely targets since the media exposure of a large, relative-to-turnover fine may be deemed draconian; moreover, the woolliness of the British DDA legislation (1995, part 3) which suggests '... reasonable adjustments to the way they deliver their services so that disabled people can use them.' is very hard to pin down at a qualitative or quantitative measure of accessibility compliance.
All of which, I believe, leaves it up to accessible developers to exhibit methods and examples of best practice to the commercial world in the hope that the message will percolate through - to not merely businesses but the design and development houses they might engage. Best practice in commercial terms being financial benefits of standards-compliant, accessible development.
Closing the Gap ... but Slowly.
There is a point in any movement when it reaches critical mass, a point when it becomes formidable and quick to growth. Some suggest that figure is at the one percentile mark. We're not there yet since there are tens of millions of web developers worldwide and, as the Web is largely ungoverned in terms of content and any vaguely competent individual can up a site, this figure will only grow as the Internet enters more corners of the world at its astonishing pace. But in terms of visible, as in, marketable, professionally sought business assets, I believe the growing legion of accessible web developers is closing the relative gap.
Web development as a marketable skill has matured, with expectations and return metrics for business more accurately defined thanks to the likes of Google and search engine technology. Coupled with the analytical software and web marketing posts emergent across a wide spectrum of businesses, it is clear the power of web marketing is being taken seriously. A closely fought competitive market hones the executive mind; accessible development gives the competitive edge.
Heady Business Cocktail
It is possible to monetise standards-compliant development; it is feasible to extrapolate from averaging population impairment the current accessible market worth - close to a trillion dollars worldwide; and it is exciting to put these two considerations into a shiny canister, shake it up and decant an intoxicating business cocktail: market-loyal repeats, web visitors who will return to a site because of standards-compliant, accessible markup.