Coke deserves a much higher PE than its bottlers because:
1) Coke's return on invested capital is much higher. Thus, when KO and its bottlers expand, KO ends up producing more free cash flow.
2) Coke's financial position is much better than its bottlers.
3) When coke hits on rough times, as it did over the past few years, it still makes a mint. The bottlers mostly show losses over the last couple of years.