I don't think any of these things are reasons to have the driver on the train. The train drivers could be located at a remote location and still be aware of these things. Loss of connectivity already means it's unsafe for the train to continue and must stop, as it cannot be aware of signals or hazards ahead.

As far as foreign objects or track failures go, these are not promptly apparent from the cabin anyway. CCTV on the track and crossings ahead is better placed for early warning.

Additionally, remote control of trains could potentially be more safe, as it would be easier for a new driver to take over in the event of e.g. the driver having a heart attack or stroke.

I think the only remaining reason is the physical accountability of being on the train.