Main reason POE is useful is that it lets you deliver power over existing wires.
If you are running new wires, you can already do what you want.
They make plenty of fiber+power in single cable, because the fiber is unaffected by the power.
Running 1km of slow, expensive, single-pair cable to run low-data rate + power, vs fiber+power cable saves you essentially one connector.
For very high cost - in money and loss of bandwidth.
Plus 10base-t1l is not common, so the price of equipment is high as well.
They make plenty of fiber+power in single cable, because the fiber is unaffected by the power.
Running 1km of slow, expensive, single-pair cable to run low-data rate + power, vs fiber+power cable saves you essentially one connector. For very high cost - in money and loss of bandwidth.
Plus 10base-t1l is not common, so the price of equipment is high as well.