>>48698731Because the amount of effort it would take to demake Gen 3 into the Gen 2 engine would be far larger than most romhackers are willing to put in. Furthermore there are a lot of hard caps on the gen 2 engine due to being a Game Boy game. Things like the Pokemon ID or move ID being saved as an 8bit integer (meaning a max value of 255) so having to go through and change that would mean rewriting the entire game; it's not just a matter of changing byte to smallint; they did a bunch of bitwise operations that would need to be redone, and then thoroughly tested. It's definitely possible, but it would take so long for one person alone that they'd probably give up.
