because that's what Child's Play is?
It's always been on the campy, somewhat self aware side of the horror genre
The first three Child's Play films were legit horror films. The first, in particular, is quite scary, or at least it was in 1988. The two sequels tried to be scary, even if they were too poorly written to be. It wasn't until the 4th movie, Bride of Chucky, that the franchise took a hard turn away from scariness and toward camp and humor. That lasted for two films until the series went back to its horror roots with Curse of Chucky. There are more films in the franchise that have been horror than have been campy, so I wouldn't say that campy epitomizes the series, though I can't blame anyone for believing that, since that's the image that it held for a long time.
For anyone who hasn't seen them yet, I recommend the two most recent films, Curse of Chucky and Cult of Chucky. They're surprisingly decent for 6th and 7th entries in a horror franchise and even hold 76% and 77% critic ratings at RT.