For me, it must have been 20 years ago in 2005. I got Kingston’s 512MB flash drive for a Christmas present and oh my how great it felt to hold so much of memory in my pocket. After that it was clear to me that there is no use for floppies to me anymore.
Around 2013, when I was just 13, on the computer at my grandparents place. I had to actually ask around and spend effort to find floppys since by then they were already obsolete, but my grandparents PC only had a floppy drive available. I used it to attempt to write an OS (I know I know, daunting task but I didnt know how much I didnt know). I got as far as writing the bootloader and got it to load and print Hello World, but no further.