See, it's no secret that that train having least occupancy in New Delhi Kanpur Route is Kanpur Shatabdi.
People of Kanpur are preferring Vande Bharat and Tejas over own Shatabdi for obvious reasons.
Unless and Until there's a concrete proposal to extend Kanpur Shatabdi to Chandigarh or Ludhiana for the benefit of Kanpurites I don't see occupancy increasing in foreseeable future. Even departing Kanpur Shatabdi after Rajdhani Gang from New Delhi side would be a boon as people would have a different option (works well for Jaipur). Or diverting it via Mathura, Agra...
more... Could work till some extent.
Of course to have any occupancy, the timings have to be far off from existing Vande Bharat and Tejas Options.
I don't mind it getting extended to Prayagraj as:
1. Kanpur will free up Pitlines. Blame of less occupancy won't be a Burden.
2. Fatehpur would get a Premium Connection
3. Since timings at Prayagraj would be relatively odd, chances of Kanpur retaining desired number of Seats would be high without any sort of maintainence responsibility.
4. Prayagraj would get a less convenient but reliable option to catch Rajdhani Trains from Delhi towards South as punctuality of Varanasi Morning Vande Bharat from Prayagraj is still dicey.
I'm not able to see extension of Shatabdi Express to Prayagraj as a genuine loss to Kanpur maybe except during Festival Rush Seasons. Maybe you could shed more light on anything I'm wrong about.