Why doesn't the primary LSO use PLAT camera?

[xnomad]

I've been watching a few LSO youtube videos and something I don't understand is why the primary LSO doesn't use any tools or references other than his eyes to gauge the glideslope?
The backup LSO stands behind the PLAT but they are just the backup.
Why does the primary use just his naked eyes if the PLAT Camera gives you the approaching aircraft position without any error?

 

Surely calls based on what you see on PLAT are going to be more reliable and superior to a human judging distance, approach angle, altitude etc?

Even if there is a reason why PLAT isn't preferred surely a mix of both where he glances down briefly would also be better?