Simple reality is that the ticket revenue does not pay the running costs of the subway (let alone the modernisations costs which were funded separately) - and so therefore all focus is on getting through with little extra cost in recruitment and training.
Many of the stations are already operated by single staff member (with a travelling relief for break cover). There is minimal shift overlap in the middle of the day.
The Sunday pattern relates as others have said to single shift pattern (bear in mind the staff work before and after public opening times to test fire alarms and distribute staff around the system) and indeed when extended opening occurs at Christmas, some of the staff will work close to a 12 hour day. That is clearly not sustainable on a week to week basis.
There can absolutely be a better subway service and more staff recruited. As with so much, SPT do not want to pay for it. People can draw their own conclusions over a relatively contained project which shows no signs of inching towards completion over 12 years since the first works began.
Cynics have pointed out most ATO systems with platform edge doors (a key requirement for UTO) are built as such - ie straight and level platforms, and the degree of accuracy needed to align with the train doors will be more challenging to achieve than anywhere else due to the geography, and question whether the system will ever be fully UTO.
There is an interesting podcast (a fair bit of marketing fluff) but also some interesting interviews with staff delivering the project.
Business · 2023
podcasts.apple.com