Some are fortunate to be in a slice of Intel where their customers, coworkers, and manager are good.
Some are protected by their manager from legitimate criticisms by their peers and customers. Since there is no consequence to their mediocrity, they stay (and unfortunately for Intel, they are often given key roles which negatively impacts the company).
Some are close to retirement, and want to get to that finish line with retirement benefits (and if they are really lucky, a nice 2016-style retirement package).
Some are wed to their routine and don’t want to stir things up and deal with the stress of a new job.
And for some, they are fearful of the outside because Intel is all they have known.