<abbr> has always been interesting to me. I've been aware of it for as long as I can remember, since it's been in all the tutorials I remember reading as a teen, and other docs as I got older. Unlike some other forgotten elements, it's one that's clearly very useful, and yet I can count on one hand the amount of times I've seen it used in the real world (yet plenty of times where someone has reinvented it with JS)
Likewise, image maps. Remember messing about with those when I was young, but Wikipedia is the only place I've seen them used. To be fair, the UX isn't great, and I've often ended up navigating to an article when I was expecting to view the image page instead
Everybody was using imagemaps in the 90s because it was the only way to have multiple links over an image, something we wanted to do because without CSS we could not have a row or a column of buttons with fancy colors and fonts and placed where we wanted them to be. So nav bars were a large image with imagemap anchors placed over the buttons.
Then we got CSS, tables (used for layout!), divs with positioning and eventually the features that web developers are using today.
Likewise, image maps. Remember messing about with those when I was young, but Wikipedia is the only place I've seen them used. To be fair, the UX isn't great, and I've often ended up navigating to an article when I was expecting to view the image page instead