Here in Zurich, lots of people commute on old steel road bikes.
They call them "Bahnhof Velo" because it is the kind if cheap bike you can ride from home to the train station and leave it there locked all day without the risk of being stolen.
Me, I prefer a commuter that allows you for wide tyres, mudguards, kickstand and chainguard.
Initially I took a hybrid bike with front suspension and flat bars, it was functional but not the best setup.
I am used to road bikes with no suspension and drop bars, so I sold it and built me a commuter based on a alu cyclocross frame with carbon fork.
That setup made a very good commuter, quick and light even though it had a triple setup, mudguards, kickstand, racks, wide touring rims etc.
Its only bad points where 3, the alu frame gave a harsh ride that could be tampered with the fat tyres and a sprung brooks saddle, no embedded mounts for racks, mudguards etc, that could be solved with clamps but they never gave a solid mount for heavier loads, and finally the cyclocross frame had a racing geometry, so, high BB, short wheelbase and head tubes, that is great for cyclocross but not so good for a city commuter or touring.
I have then swapped over the frame with a Salsa Casseroll and I am now fully happy with it.
Steel frame and fork gives a nice compliant ride, built in mounts for everything, and a touring geometry, with low BB and longer wheelbase and head tube, simply great overall