Uhh... Granted, I haven't been into the hobby all that long, but has there ever in the history of RPGs been any lines that DIDN'T release books to give players new abilities*? Hell, "splat" as a term for books offering player options is originally derived from White Wolf's WoD, if I recall correctly, as shorthand for their ubiquitous Clanbook/Tribebook/Whateverbooks that were released for every game. I know 2nd Edition had a ton of those Quintessential Fighter and similar dealies, and I've no idea what a "kit" is, but from what I've read it sounds like it was just extra options for players.