Firstly, I don't think it's always avoidance.
There are two main culprits out there which stop people eating a healthy option.
Firstly, there's convenience food:
There is too much out there that is branded as convenience food - eg, ready meals - which are seen by many as an 'affordable option'.
These are chosen over eating a eating a healthy, balanced diet, because they're cost effective for those on a tight budget and may well be the affordable option, but are rarely a healthy, balanced option.
On the other hand, there is fast food - burgers, takeaways etc.
These are definitely tasty and are identified with from advertising - because everyone shown is healthy and enjoying themselves, but they're rarely the healthy option when used as the primary source of nutrition.
Often this food is eaten because it saves having to prepare food in advance, but worse, those who eat it get into a rut where they feel the don't have to prepare their food anymore. What they don't appreciate is that what they're eating is not providing them with that healthy, balanced diet.
So in some cases, it's laziness that is the issue, sometimes it's time and sometimes it's not having the budget to afford healthy eating.