As far as fast-casual restaurant concepts go, Shake Shack (NYSE: SHAK) lacks many of the characteristics Wall Street usually looks for in its favorite stocks. Customer traffic isn't surging higher at existing locations as it did back in Chipotle's (NYSE: CMG) high-flying days in 2015. And profitability is declining, rather than rising as it has for McDonald's (NYSE: MCD) over the past few years.Yet Shake Shack stock outperformed the market in 2017 and is valued at a significant premium over peers like Chipotle, McDonald's, and Yum Brands (NYSE: YUM).Let's break down the two biggest reasons for this valuation gap.Continue reading