I agree, in fact new ones have come up recently. Easyjet created a package holiday service website in the last few years too... Thomas Cook may have survived if they had put more of their business online.
Its more the older generation that don't like or trust using the internet that will still use traditional Travel Agents, but they won't be around much longer.

Like you said, the industry is changing, and if a business doesn't change with it, it will be doomed.