In my experience, bad eating habits for kids are formed when their parents let them eat what they want from a young age (this usually translates to 'white food' - lots of pasta and cheese and other non-threatening fare), and are too lazy or want to avoid saying no to their kids' desires.

For example, my poor nephew has all kinds of food issues.  He really does prefer to eat pasta, potatoes, cheese. lots and lots of dairy - but is forced to eat some other stuff for his health (which he's quite aware of).  Dairy in particular disagrees with his skin problem.  But I watched him growing up, his parents (mostly his mother) never gave him ANYTHING he didn't want to eat, so he ate mostly pasta (no sauce just some cheese) and milk. At 8, he was always constipated and had to get into prune juice to overcome that.  

I'd wager that most poor eating habits for kids develop as noted above.  Hard to blame either parent particularly for it, rather poor child-raising advice from 'experts'.