My first experience with xDSL was HDSL, about 25 years ago. It was symmetrical and used to carry a DS1 (T1) at 1.544 Mb/s.
ADSL is asymmetrical, to provide the best balance for typical users, who generally receive much more than they send. This is also typical for many businesses. With cable modems, over copper, there are real limitations due to how bandwidth was allocated over the cable. The upstream traffic was originally below the lowest TV channel frequency. I don't know what happens with DOCSIS 3.1, which uses Orthogonal Frequency Division Multiplexing, instead of the fixed 6 MHz channels of previous versions.
Balance upload/download is more important with larger businesses that have VPNs between sites or servers.
I haven't lost my mind. It's around here...somewhere...