The set of real numbers is continuous and uncountably infinite. Any attempt to fit it into a discrete finite set necessarily requires severe tradeoffs. Different tradeoffs are desirable for different applications.
Almost All real numbers are non-Computable, so what we're most commonly reaching for is only the rationals, but the thing is DEC64 can't represent lots of those, it seems like a very niche type rather than, as the author asserts, the only numeric type you need.
