The asymmetry stems from the days where we connected through the phone lines, which was not designed for data. There it was possible to have a higher bandwidth out from the phone switches than in. That is, dial-up modems and DSL modems could have a much higher download speed than upload.
I don't know about cable, but I suspect it's the same there.
OTH, fiber-based internet often has symmetric speeds. Don't know the stats, but I suspect most fiber ISPs gives you that.
