United isn't the only airline that won't notice when a regular leaves. I was Solitaire on SQ for 14 consecutive years. I often paid more to fly them because I was going for Lifetime Solitaire. Then they cancelled their Lifetime program. So I switched to United to save money. One might expect that when a flyer has been at the top level of their program for 14 years and suddenly quits flying someone might ask "why?".

Nope. Apparently they're still not aware that I'm gone.

The reality is that these are huge companies and the loss of a customer who spends $20 or $30k per year won't even show on their spreadsheets.