What does scroll lock even do? I've been using computers for about two decades now and I've never managed to figure it out :/
There are a very few programs that use Scroll Lock. Agent/Free Agent newsreader (for Usenet newsgroups, if you don't know what that is, don't worry about it) uses it. Normally, when you push up-arrow or down-arrow, the cursor moves to the next line up or down. With scroll-lock on (at least in Free Agent), the cursor line and all the text move up as one, just like clicking on the up-arrow or down-arrow of the scrollbar. The cursor stays on the same line of text, but everything has moved up or down. To get back to regular cursor up-and-down movement you press Scroll Lock again (it toggles, just like Caps Lock, Num Lock and Insert).
This was an original feature of the IBM PC and its original keyboard (which was the first to have the "scroll lock" key), and this was well before fancy screens and "scrollbars" were available on personal computers, but not many programs used the scroll-lock feature even back then. Many programs were converted as-is from CP/M, and people were happy with them even on the newfangled IBM equipment.