It's their call. Savannah GA's CBS affiliate WTOC and Huntsville AL's WHNT also don't use the eye logo in their IDs.
Boston 25 does the same thing. Since 25 was sold to Cox from Fox. They do not acknowledge during their newscasts or station ID that they are a Fox affiliate. Only when a Fox program is on is when you know they are Fox. Also in Bristol county, on Comcast, Boston 25 is blocked during Fox programs. You have to watch Fox Providence which is their station ID.
I have noticed for many years that WPRI never seems to use the CBS eye logo in the station ID. Most stations these days seem to use their network logo long with their channel number, so I wonder why WPRI is an exception?