Gotta agree to disagree here. You seem to be arguing for the Kerry election strategy per Bob Shrum which is to only concentrate on the bare minimum amount of states needed to win the election. Great if you run the table but not so much if you get a surprise (Ohio, in the case of that election which apparently they were counting on).
If a candidate is going to completely write off in no particular order NC, GA, FL and AZ to name a few recent wins and near misses, then not only do they give up any margin of error, but the GOP can then conserve resources to defend the states that they need. I want a nominee that can force Chump to defend NC so that it doesn't turn into VA for them, and one that can find that extra .1% of the vote in Florida that we've been losing by lately.
I'll also note that while Sanders won the MI primary, which a lot of his fans hang their hat on, he also lost the primaries in PA, OH, FL, IA, VA, NC etc etc - meaning his primary state victories didn't show a path to victory in the general election either.