There's nothing stupid about it. Other standard floppy disk images do not include checksum either. Its primary function is to preserve integrity when reading the disk, which is entirely unnecessary when we're no longer using the unreliable floppy disk medium to preserve it. Your hard disk has its own CRC already.
Is there some game that you want to emulate that does something meaningful with a bad checksum? It would be nice to know an example of this so that we're not just speaking hypothetically.
Similar question for gaps. We can complain that gaps are missing from the format, but what problem does putting them in solve? A naive dump will just fill the gap with whatever bytes it reads. A real gap can be full of garbage not representable that way. If there was theoretically some copy protection scheme that relied on tricks with gap encoding, I'm certain it wouldn't be solved by just copying bytes read from the gap verbatim. That'd be an incredibly weak attempt at such a thing. More likely we'd get things like strange encodings intended to confuse the reader/copier, or something that relies on specific data timings, which would need a lot more than just a naive gap byte dump to encode. Floppy disk formats I know of that encode information that's useful for copy protection emulation tend to be insanely complicated... a series of strange additions, each one to address a new creative method of protection that was found. You can't can't future proof your format for this stuff, it just has to be extensible so you can keep adding to it.
So what's stupid about a straightforward format that correctly encodes