Mobs have short follow/target range

All hostile mobs that want to attack the player only can see the target in a short distance.
Some mobs can see further than 16 block radius like ghasts but it isn't the max attack distance.

Steps to reproduce:

1. Summon a mob(e.g. husk, ghast)
2.  /gamemode survival
3.  Run 16 blocks away and the mob cannot follow you.

Observed Results:
Mobs stop following the target if they outer 16 blocks. It causes ghasts to not expect the player, vexes cannot chase the target and you can see this bug in many other mobs.

Expected Results:
Mobs should follow the target a little bit farther than 16 blocks.

Code Analysis:
This comment.
 

Videos:
https://drive.google.com/open?id=1pnx2w6YvCHnyPH4nS-Ihgulpt1GsLeQC]

https://drive.google.com/open?id=1P6WJ1mgt9jwMtOSI2-n3eB2ofy5HiHyN