Didn't QF inherit the 717s from Impulse? Didn't think it was a conscious decision to acquire them. When Impulse got them the EMB135/145 were the rage of the day and C605s, etc for RJs. Since they're a MD product I'd suspect they got a good deal on them since MD was one foot in the grave in those days.
Even so they could have sold the silly things but since I'm not a math grad or a bean counter who knows what Mngt was thinking other than 'too expensive'.