Why is Asus so slow with security updates?

[v3l0ct]

I'm still on the Dec 23 security patch and Google Play store is on Nov 23. Why is Asus horribly slow at updates? I really like the phone but unsure I'll keep it long term if it's not going to be updated. Is it similar to OnePlus who updates every other month? 

[kickner96]

I'm much more confused, why the Google Play Services are still on Nov 23. Thought those updates are coming directly from Google?