I've got very mixed feelings about this. My natural inclination is to put this down to neglect/laziness, but then I started thinking a bit more and I think it's much more symptomatic of various things that have gone wrong with our society.
Yes, there are always going to be cases where poverty/poor parenting applies, but in the case of working parents there is a bigger picture to be looked at I think.
Apparently we are working longer hours than ever, despite (or possibly because of) technology. Couple that with the amount of children now being schooled outside their catchment area and the travelling that involves, and for some parents factoring in enough time to make sure the entire family sits down and eats breakfast together would mean getting up at 5am! With the length of the school/working day (including commuting), the emphasis on homework and extra-curricular activities for children and the usual demands on adults, and getting to bed at an early enough time to allow for such an early start is near to impossible. So it becomes a choice between breakfast and sleep deprivation. What's worse? The intention to send in mid-morning snacks probably helps most parents rationalise this, and it's a lifestyle choice being endorsed by the food industry and a situation where many adults forego breakfast altogether for various reasons.
For parents who can afford it, the solution is to move nearer the job/better school to save time, have a SAHP, or enlist the help of a willing relative or paid professional, but many people aren't in that position.
I still think a lot of it is skewed priorities and laziness, but to be fair to some of these parents, it's easy to say "make this your priority" but far harder to do it when there are so many other 'priorities' being demanded - such as earning the money to pay for that food in the first place, reading to your children (also something that only takes 10 minutes and should be done daily), etc.
I don't know what the answer is and while my children have gone to school without breakfast on occasion (because they refused to eat anything), it's never been because I've been "too busy" to make it available. Despite working full time, mornings are quite relaxed in my house.