They want to see if anyone will ever 0-day their system.
To be fair, I have old MacOS laptops that are my wife's laptops, we keep them around because they still turn on, and they have all her old files (I've backed it all up several different ways for her), but I never go on the web with any of the browsers installed on those systems.
I know, there pretty nice Linux distros that are lightweight and snappy too. One day... :) but not yet :)