The discouragement factor.

One of my more recent forays into the strip archives yielded an interesting result; as you may or may not know, Mike and Brian had tried to show Elly the result of a fairly intricate piece of computer programming. Instead of marveling at the skill required, Flapandhonk whipped out a flip-book, showed them she could do much the same thing they did by hand and declared what she doesn't have the patience and brains to use useless. This might seem like a random act of idiot bitchery were it not an example of a pattern. To put it simply, Elly actively discourages her children from exploring careers she herself cannot or will not pursue. Let's examine this in closer detail on a case-by-case basis:

• Michael: As we all know, Michael used to not only be fairly interested in computers, he loved playing peewee hockey and probably had fantasies of being the next Gordie Howe. The problem with that is that Elly needed him to be the author of the family; y'see, she didn't have the brains, talent, stamina or discipline to do anything other than create a leaden poem that had the self-serving premise "Apologize to your poor, put-upon mother for wanting affection." It therefore became Priority One to make sure that Mike produced the Great Big Novel that would allow a sullen, bloated and imbecilic failure to bask in his reflected glory; she awarded herself bonus points for keeping him away from the evil devil machines that confuse her and the terrifying sports that bore and alarm her.
• Liz: One of the things we tend to lose sight of is that Liz used to be into figure skating when she was ten or so; as a matter of fact, she also sort of vaguely resented how the city caved in to her insane, ignorant mother's demand that the EEEEEEEEEEEvil sports stadium not be built. It's a good thing for Elly that Liz is slightly more in need of parental approval than her ugly brother; that made it easy for Mommy to slowly convince her that sports were un-feminine so that she might become Elly's ideal teacher: a glorified baby-sitter who coddles a discipline problem and doesn't dare correct bad behavior. Simply put, the world has one useless teacher the more because the bane of a competent educator's existence had been allowed to reproduce and raise children. Also, Elly cannot skate and, on the dance floor, tends to trip over her own shadow.
• April: While it's sort of true that April came up with the idea of being a vet on her own, it's sort of obvious that it's not really her idea that music is a foolish affectation; she's just doing it because she gets anti-music propaganda from both sides. John's antipathy probably stems from his taking a social back seat to some guy with a guitar but Elly's is far more repulsive. Y'see, she freaking hates it that Phil, her younger brother, is known and respected by the media as a name in the jazz community while she, the older and 'smarter' sibling, is an anonymous housewife who's never going to be anything more than the subject of off-color jokes about crazy old women.

In all three cases, we have Elly selfishly tearing down those 'who can' because she can't stand being reminded that she doesn't have the patience or inclination to be one of them; the end result is that we have two misfits who think that they're happy doing jobs they're not good at and a third not getting any respect because her horses can't take Elly anywhere.