It would seem obvious that the institution should set a set of standard conditions for students and supervisors, but this seems not to be the case. The tradition seems to be that each student is expected to negotiate with their supervisor. This seems an unrealistic and inequitable practice. There are limits on the resources which the institution can provide (essentially eight minutes of their supervisor's time per week). If the student expects more, then the cost of the extra resources will have to come from elsewhere. The supervisor may have a funded research project, with the student working as a research assistant.
It strikes me that mature students who have come from a workplace would benefit from being part of a familiar structure. It may be useful to have the students working as part of a team. This could be encouraged by funding agencies in provision of research funding.