Wow, Ironbutt. You really can't understand simple concepts, can you?
Put as simply as I can so that even you can understand, if airlines treat pilots simply as a commodity whose experience and qualifications count for next to nothing, that endangers flight safety.
If pilots permit CX (or any other airline) to get away with such behaviour, it will persist and worsen. If, however, such treatment results in pilots refusing to take jobs with the said airline, they are more likely to modify their attitudes and management techniques, resulting in a safer airline.
Further reasons? Anyone who is not totally self-centred will be able to empathise with the plight of a fellow professional who has been shabbily treated by a major player in the industry, and will have the opportunity to register their disgust.
And more - CX F/O's who avail themselves of the opportunity of a command under the circumstances you describe are taking jobs that rightfully belong to pilots unjustly fired.
Would you merely shrug your shoulders if your employer sacked you on a trumped-up charge and an FO with whom you had been flying merely looked upon your dismissal as a command opportunity, and took your job, leaving you to wonder where the next mortgage payment was coming from? Or would you hope that he would support you in any case you were to bring for unfair dismissal?
So there are a few reasons:-
1) Flight Safety
2) Professional Courtesy
3) Lack of Selfish Motivation
4) Simple Humanity
Which of these (if any) don't you understand?