Why Do Characters in the anime Refer to All Pokemon as "It?"

I don't know. It is annoying though. Sometimes they'll refer to the gender like in "Memories are Made of Bliss" Dawn hugged Piplup when he was about to cry and told him, "You're a big boy." Also, in "Diancie and the Cocoon of Destruction" when Argus was watching Diancie on video he đã đưa ý kiến "If Diancie escapes we'll never be able to find her again." hoặc something along those lines, but Argus did refer to Diancie as a girl.

Probably because they don't know whenever it's a male hoặc a female. Although i do find it odd that they continue calling a pokemon an "it" when its obvious it's a male/female