Those are really good and reasonable questions to ask. In a perfect world, any outpatient child that is reasonably developmentally intact should have a comprehensive evaluation prior to putting in a feeding tube. And those that are not developmentally intact should have even more evaluation and testing. There are lots of reasons why children have eating issues, from difficulties with texture and swallowing, regurgitation, aspiration, to simple "behavioral" issues of refusal of foods, or other behavior issues surrounding eating (tantrums, intentional gagging, etc). And the entire picture of their medical and behavioral conditions has to be taken into account during these evaluations. A child with behavior issues needs a completely different approach than a child who has, for example, a profound neuromuscular condition, or cancer treatments.
Here are some examples of these types of evaluations:
http://www.marcus.org/Menus/Document...ningForm08.pdf
http://www.choc.org/files/Feeding ...stionnaire.pdf
http://faculty.caldwell.edu/sreeve/E...ssessments.ppt
The reality is that a large proportion of these kids have the feeding tubes put in during an inpatient admission for some kind of exacerbation of their underlying condition. They may have had failure to thrive and feeding issues for a long time, but the hospitalization becomes the tipping point where the g-tube becomes a reasonable option long term. This is one instance where "to cut is to cure" often proves possible-- enteral feeds produce rapid improvement in the child's overall picture.
Once the tube is placed and the child is improving, there is reluctance to remove it, or pursue a bunch of testing to see how to transition to removing the tube. If the child is "ill enough", there is inertia in the will to get the tube out. It's circular logic-- the child improves, therefore the tube and enteral feeds are necessary and important to their care. And if the child DOESN'T improve (gain weight, etc), then no one will seriously consider removing it once it is placed.
In the case of medical child abuse, once the tube is in, there are lots of reasons why the parent may justify leaving it in for months to years, and doctor shop to find one in agreement.
And for kids who are actually sick, or have developmental or behavior issues, the parent is often relieved to be free of the burden of the hours and hours devoted to complex and frustrating feeding issues, and reluctant to go back to the way things were before the tube was placed.