It has nothing to do with laziness in typing.

It's just not wanting to keep track of more rules. If you've only ever used languages where a leading decimal point is allowed, it's a pain point to suddenly have to remember that it isn't here, and for no obviously intuitive reason.

It's about wanting to avoid unnecessary conceptual friction. Not lazy keyboard usage.

(Heck, your second example uses an extra keystroke. And it's perfectly readable to me, based on the languages I use.)