By the way both recently introduced Ghazipur trains Suhaildev express and Ghazipur Bandra trains have the same quota for Jaunpur as for the terminating station (i.e., Ghazipur), so I would consider them 'direct' trains for Jaunpur.
So your explanation for no trains is just based on the issue of pride (that important trains should terminate in Jaunpur) not demand.
You can demand for extension of Shabd Bhedi from Ghazipur which is totally valid and justified as it runs mostly empty for Ghazipur and it would be highly beneficial for Jaunpur