I still don't understand why SH4 isn't popular for modders

This game has potential to be better platform as U-boot sim than SH3 - better graphic as stock game than modded SH3, crew watches system, good repair system, full pack of U-boot types etc. Using OM+OMEGU this is a quite good piece of work, much better than bugged SH5. Is it more hardcoded than SH3 and SH5, is it more difficult to create mods for it? I like SH3 with GWX very much, like first love, but SH4 with all mods created for SH3 would be kick-ass game.