One point is that each commute and commuter is different.

A lot of bike commutes are say < 5 miles each way, with alternatives such as a spouse to call with a car, or bus services. If say one breaks down halfway, that leaves about 2.5 miles which one can limp the bike along, or walk, or perhaps even drop off at the nearest bike shop.

I don't ride every day, but my "commutes" and utility rides are typically 20 to 40 miles RT (with a few much longer). And I'm very much self supporting. If I break down, I fix it on the spot. Buses are inconvenient for me at best, and nonexistent for the last 5 miles or so.

Critical failures 20 miles, or 70 miles from home can be stressful.

So, while one bike commuter may simply need a parka, then next will need rain gear designed to keep oneself dry from rain, and dry from sweat.

One may figure they can do without a pump or spares, the next will need pumps, tubes, chain tools, etc.