Originally Posted by
Random_Flyer
When both airlines offer the same configurations, then you'd be more likely to see crossover. But when airline A offers a feature airline B does not, why should airline A give that feature away to airline B's customers when airline B has nothing to offer airline A's customers?
Your point about US not offering an E+ equivalent is well taken. However, US does have exit rows and bulkheads (legroom!). Granted, there aren't a whole lot of those seats, but other *A members offer their exit rows and bulkheads to *Golds.