The reason why Spicer cannot laugh it off is Trump. Trump does not want his communications people to admit any mistakes or missteps, and to attack anyone who disparages the POTUS in any way. Why else would he be shaking up the staff and bringing in people like Lewandowski? Had Spicer made a joke of "covfefe" he would likely have been dressed down by the Commander in Chief. Plain and simple. And, yes, his is a job no one qualified seems to want.