To be clear, I'm from Spain, and that loyalty is still a selling item among 40-and-over. Also, seniority is a plus almost everywhere, where you can win arguments with "I've been working here twenty years", even to people the same age than you but with less seniority. Going to other place even with higher salary is a loss for lots of people.
But youngers doesn't care, and I have the impression they actually fear being for too long, say more than 5 years, in the same place. They value the novelty of knowing new people and ways to get stuff done.
That only barely worked when corporations were a little bit loyal to employees. There's not one of those left now.