Accessibility cuts both ways, though. Choosing to prioritize the HTML-only version decreases accessibility to people who have limited bandwidth or download speeds.
This surely hasn't been a major problem since probably the 14.4k modem stages for typical sites, and, even if it was, wouldn't limit accessibility (except in the sense that it'd delay viewing by a few milliseconds->seconds). Especially when the majority of the bandwidth cost will be data that has to be sent regardless (maybe with a necessarily increased amount of metadata).