(Strip Number 209, Original Publication Date, 4 January 1982)
Panel 1: As Elly and John arrive at the ticket counter, Mike says that he sure wishes that he and Lizzie could come with them. Lizzie echoes this by saying "Wanna come wif you!!"
Panel 2: Elly does more parenting in 2.5 seconds than she did most of last year by actually looking a crying Lizzie in the eye and saying "I know you do....but not this time."
Panel 3: As they walk to the gate, she asks John if he feels guilty for leaving the kids behind; he says that he does....
Panel 4: ....but he'll live with it. The reason he's supposed to be able to live with it is that the kids are already at each others' throats but, well, there are other reasons.
Summary: The reason that most readily occurs to me is that even a more responsible parent who took the time to explain that he did know that his children felt as if they were being abandoned or deliberately shut out of a good thing and did allow as how long it would feel and even explained that this was nothing personal and managed to get his point across would still feel regret about his going on vacation; he wouldn't let that guilt consume him or allow the prospect of feeling guilty become such a crippling thing as it is in the Pattersphere. We've seen too many examples of Elly thinking that being made to feel remorse is The Worst Thing Ever to not know that someone's narcissism distorts how she behaves.