1. I want to see color output in some commands, but not all of them (in some cases like with grep/ag it is very useful, in some cases colors are not useful or even makes it harder to read command output). NO_COLOR allows me to control output per-command by creating aliases 'env NO_COLOR=1 command'

2. Some color-using CLI tools assume white-ish background and actively use dark blue which is hard to see on a black background.