It would. And the need for station staff will reduce with more online sales and the likely introduction of contactless etc.
TBH, I would trade ticket office staff for a TVM that did TOD. I'm sure many others would too.
Merseyrail's Concession Agreement with Merseytravel states (in section 6 of Appendix A of Schedule 18 (Customer Service Regime)) that:
"All ticket offices at all Stations (other than Unstaffed and Ellesmere Port Station) should be staffed from 15 minutes before the scheduled time of the first First Train to 15 minutes after the actual departure time of the last Train or replacement service, seven days per week."
Thus, Merseyrail can not reduce the ticket office opening hours without either breaking its Concession Agreement or getting Merseytravel to agree to a contract amendment. Any Merseytravel agreement to a contract amendment for this would presumably include an adjustment to the amount of the Contract Payment, and any such adjustment may well equal (or even exceed) the savings from reducing the ticket office opening hours.