1) I wont cry if it gets stolen, and built from old recycled parts, who'd really want it except maybe a messenger type- and if they want it bad enough, take it, I'll just build another.
2) With only 1 gear and 1 brake, its light, and low maintenance (once a month oil the chain, and thats about it)
3) Good training that doesnt feel like training 'cause it's just fun, but my spin is much better, and rolling over the few short hills to work in a higher gear than normal makes me stronger without thinking about "training"- I'm just cruisin'
4) Handles better than a freewheel bike in slippery/icy conditions, and no worries about getting it wet cause like, it's recycled junk. Spray paint and axle grease in the bearings.
For commuting every day, keep it simple- you dont wanna be constantly tinkering/cleaning/adjusting/pampering a bike you paid real money for. Find an old frame in your size with horizontal dropouts, and have at it. Put on some cheap fat rimmed wheels to eliminate flat tires. Heavy wheels make you stronger- really! Most bikeshops have junk parts bins you can rummage through, or just watch the Fall-cleaning sidewalk sales in any suburban neighborhood- it's amazing what people throw away. I gotta admit that I did splurge and installed a pair of original eggbeaters on mine though- they are fantastic, easy to get into/out of, light, low maintenance. I race cross on them too- no more Time or spd pedals for me!