It has pretty much been around since the original computers came out.It comes from people that know how to code. The jtag wasn't an accident, it was made specifically for modding/hacking.

The Way I find about hacking is that someone finally got there hands on a computer and looked around the internet and found certain coding languges and i believe they mixed them together to make them lines of code which then evolved from an idea such as I would like to control my friends computer without them knowing and such yet I believe modding was found in the same way and computer editing to place new parts has been round for ages someone must of been smart enought to look inside there xbox used the ways to connect it to the computer and made there lines of code and transfered to the xbox dosen't sound hard but the effort of learning a new coding languge can take weeks, months even years to learn so one smart guy ehy

Maybee they wanted to try something new ? Think outside the boxx ..? People have always tried to mod things ..