Why do so many people think WTD break = 30 mins per 6 hours?

UK PROFESSIONAL DRIVERS FORUMS THE UK PROFESSIONAL DRIVERS FORUM (INTERACTIVE)
19

LEGAL WTD EXAMPLE where driving time does not go over 4.5 hours

work 6 hrs
break 15 mins
work 6 hrs
break 15 mins
work 2 hrs
break 15 mins
work 15 mins