Because it made more sense in my head. I kinda didn't like how 1 skill did a bunch of stuff, it was harder to do out on paper.
The only thing Skill does is +2 hit per skill and +1 crit/2 skill. Luck is the bigger offender here, giving +1 evasion/luck, +1 hit/2 luck, and -1 enemy crit/luck.
As is, without a luck stat, crits have no way of being negated and are thusly much much more powerful, especially against the party. As well, hit rates will be lowered by a small amount, and evasion by a larger amount. Take that into account when assigning hit rates and evasion. And note that weapons were balanced towards the original system, so you may have to tweak stats on those as well.
It might just be easier to stick with stats as they were, man. :/