Many buildings already have sensors wired in to PLCs and it's easy to network with the PLC to record and display the signals (for which there are many existing "dashboards" - HMI packages of varying cost and ability).
I don't think it would matter much who owns or maintains the server if you're using a PLC to aggregate your signals onto the network. Many companies are paranoid and would want an in-house server. But it wouldn't be much different to use a cloud based instance.
It's true that existing automation hardware and software are obscenely expensive compared to consumer tech, to the point where renting/subscription might make sense for certain use cases. The systems sufficiently complicated, though, that independent professionals usually manage the setup and maintenance.