The GULO pseudo gene is being expressed in humans according to Genecards.
Why is this still taking place after tens of millions of years since then gene lost the capacity to encode for a functional enzyme?
Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It only takes a minute to sign up.Sign up to join this community
I suggest thinking about this from a different direction — something like: "What selection pressure is there for loss of expression of the GULO pseudogene?"
When thinking about that question note that the expression level is very low (less than 1 transcript in a million in the tissue with the highest level of expression.
In general, evolution is messy and I think your null hypothesis should be that this as a vestigial trait.
In other words, unless you can show that there is a significant cost for the low level of expression seen from this pseudogene there is nothing to explain.