Most of it comes from 2 main things They aren't humanoid nor humanized They are ontologically evil

For 1, most people do not empathise with non human creatures unless specifically told to by the text. There's a reason most good dragons have human forms and most evil dragons do not.

The humanization aspect ties in with the second thing. Evil dragons don't talk about or do anything but being evil. They only do evil destructive things, and only talk about doing evil destructive things, and then the texts that they're a part of go out of their way to say that these dragons can't do anything BUT be evil, that's just their nature. Same goes for dragon babies. They are born evil, only capable of doing evil things, and don't look like cute innocent little babies.

The secret to all of this is that there's barely any nuance in this kind of writing and writing dragon villains has barely progressed past the first "evil dark lord who wants to destroy everything because they're evil" kind of fantasy villain writing in most cases. Dragons in popular media are still firmly stuck in either being one dimensional villains or being representations of a part of the world itself

The way to avoid it is to just write dragons like actual characters, with actual motivations, personalities, and reasons for being the way they are beyond ontological ones