ppl's naming sense in manga sucks... i swear this is like the 3rd or 4th time someone nam...

Those are common Japanese pet names except for the slime one. That one is just adapted for English localization.

I get that the names are common. i just don't understand why these story creators can't be more creative!

I agree, but unless they are really good at naming things like me, chances are that they don't trust themselves with making unique and interesting names because naming things is hard. Plus they are on a deadline. They can't waste too much time thinking up names. And thus, a preset list of pet names was born. If all else fails, they use the list.

i kind of get it, but it still feels like an excuse to be lazy. i could come up with a unique and interesting pet name in less than 5 minutes.

Same here. But not everyone has that talent. Let's be honest here, there are people who's naming sense that shouldn't be allowed anywhere NEAR something that needs a name.
For example, I met a guy who named his white small dog "BONE TREAT!"

The male symbol was supposed to be a facepalm

lol, "Bone Treat"

Yeah, some people just have the weirdest naming sense.