Loyalty is a two way street ...
My best answer is ... it doesn't.
As one of of those old guys -- I'm in my late 50's -- that has been around long enough to have seen the advent of FF programs in the early 80's, I can provide some perspective.
FF programs are designed to create loyalty. Delta's changes over the past several years have destroyed the loyalty I once had to Delta. Rather than direct my business to Delta when and wherever possible, I now just travel on the airline that will provide me with the best value for my travel dollars.
Sure, I am grateful for my lifetime Gold status, earned because of my total program miles. Not paying for checked bags and the ability to get the occasional upgrade to Delta Comfort or First has value for me. But, ultimately, it comes down to total cost. For example, earlier this week I was looking at seats to Costa Rica: over $900 RT on Delta vs. $412 on United. With that kind of difference in fare, I'll pay for my bags and fly United.
Likewise, on a domestic trip where I may have to change my plans, I'll most often go with Southwest, as I know I can cancel my original flights and still retain the full value of the fare paid, as long as I use it within a year of my original booking.
Same Day Confirmed had caused me, for a while, to switch much of my travel back to Delta. SDC was an innovative product that provided real value for me; I used it quite a bit. Then Delta implemented the "same fare bucket" requirement which, for me, just about killed any value SDC once held.
I could go on ... the elimination of the 48 hour hold on reward tickets, the 72 hour "no changes" policy on award tickets, the "executive membership" change in the Sky Club, etc., etc.
Moves like that don't inspire loyalty.