I love talking "just like that" with people as I tend to get good info, despite getting it off the record.
I had a word with someone who handles PR for 2 netbook/notebook/laptop/AIO/Desktop replacement units company. The reason (according to them as their position is limited to PR and does not include marketing) is purely on pricing. Near decent atom netbooks cost 18-22k. Add a little more money you would get an i3 notebook from certain Tier 1 brands. Pricing is done in such a manner it just ridiculousy stupid to slot in between as people will be even more encouraged to grab a "low end" notebook against a netbook. If they do so, netbook will not do as well as it should. Also these companies are pushing tablet concept way more than netbook concept, so some companies deemed that its best not to get such netbooks and waste time and money to promote it. You might see fusion netbooks somewhere in the near future or by any chance if a company does not see things this way.
Why is it priced this way? Well that's the question where a real answer wont materialise soon.