That goes two ways - the travelling public might think that the fare isn't priced as low as its economic worth.
The sweet spot is the price that maximises the revenue, not the price that carries the most people.
Rail is, or at least ought to be, a public all day service. There is a balance of aiming to achieve this rather than not running at all where the cost of the latter would be lower e.g. a frequency of 15 minutes peak and 30 minutes off-peak rather than hourly or less. Inevitably there is spare capacity at times of lower demand.
Train specific discounted advance tickets ought to serve two purposes.
The first is to encourage those who are flexible when they travel to do so at quieter times with the objective of minimising the number of services be they peak or off-peak that do run very close to or beyond capacity.
The second is ' bums on seats ' rather than ' relocating fresh air ' from ticket sales to those who otherwise would not travel by rail at all.
The skill is setting the advance ticket prices and quotas.
Now we have moved from franchises to concessions and ( I presume ) all ticket revenue goes into a common pot then ORCATS distribution is dead what there is no need for is operator specific tickets with the objective of that operator keeping all the ticket revenue rather than sharing the number of passengers on each train by encouraging some to take a slower journey in return for paying a lower fare.