It's not just the wires reaching Leicester, I think there are capacity issues that need to be resolved too. NR published a report about Leicester last year that's worth a skim through, it does talk about a 5th service from the South eg Bedford-Nottingham
Given there are already 4tph Leicester-StP so this is really the question of demand for travel from the East Mids to places like Bedford, Lutons and St Albans.
However, the structure of the EMR timetable recast is basically saying that they don't believe it's significant enough to provide direct services and continuing with something like the current Notts semi fast... And they presumably had the ticket data?