You can think of mutual-loyalty as an extended transaction, if you prefer. If, in exchange for you not planning on leaving the company, the company actively does its best to treat you well and preserve your job long-term, that can be a good trade-off.

The mutuality is important. You absolutely shouldn't think of yourself as "loyal" to a company that won't stick up for you. (And many companies won't, to be clear. If asked to choose between cutting executive salaries by 2% and firing you, most companies won't think too hard about that. You shouldn't be loyal to those ones.)