if running MSTP with one instance why not just use RSTP?

I have been reading a little more about MSTP and production use cases and so far what i see is that you simply use a single instance with predefined vlans because it can get pretty daunting to manage instances and make sure all trunks are not pruning Vlans that are part of your MST region.

So i wonder, for such cases why MST at all, why not simply use RSTP (assuming you don't have many vlans for pvst/pvst+)?

The only scenario i see where MSTP would be useful, is if you have a pretty segmented network where several sets of vlans will always be together in the switches and the trunks related to them.

I would love to hear some real life scenarios where you needed MSTP and how you were able to manage the configuration and operation side especially with many people in the team (making sure you don't forget to add a vlan to a new device or make sure the trunk is allowing that set of vlans, etc)