When code runs slower in one JS implementation than another, why do people say that "real-world" code is slow? Just because the JIT missed an optimization-- in

When code runs slower in one JS implementation than another, why do people say that "real-world" code is slow? Just because the JIT missed an optimization-- in this case, repeatedly appending to a string-- doesn't mean that it's a bottleneck for the JS that browser run into in the wild. People don't often run jslint or jsunzip frequently, they run jquery and do lots of DOM accesses.