They do use it https://www.facebook.com/applemusic/

  > Typically replies within an hour

Damn.

Most companies have that... it's often just a bot.

They have a facebook messenger bot so thats more than likely why.

They use Instagram and Facebook to advertise iPhone's alot.

Wow, I never knew that.

Probably for ads. Since ads can be rendered as regular post a profile is needed but they won't be rendered in the profile's feed.

Apple also has an account with no posts on Twitter: https://twitter.com/apple

Apple's Twitter account is used exclusively for ads and special functionality like reminding you about events.

https://techcrunch.com/2016/09/02/the-invisible-apple-tweet/

I wonder if Facebook lets them do something similar.