I only own one set of keycaps that aren't on a board currently, and they'll be going on my next one when the kit arrives. So technically I have 3 sets of keycaps for 3 boards: DSA blanks for Diverge TM 2, stock on HHKB JP, and Troubled Minds for my upcoming Revo (they used to be on my Unit-01-themed Planck with a purple anodized case).
This is mostly because I just don't find too many sets appealing to me, if it weren't for the EVA theme with Troubled Minds I doubt i would've bought those either.