Saw Adam at a con once where he talked about the restrictions they are under from the network. He has hundreds of myths he wants to do that the network has deemed not interesting (read: explosiony) enough. The example he used was testing Monster cables versus wirehangers.
I would think they would have a significant extra amount of paperwork involved in tests involving human subjects. Even more with children, since their parents/guardians would have to sign.
And the risks to the show/network would be pretty high.
Suppose something goes wrong. Any waivers signed could be challenged in court, and likely wouldn’t stand up (if something went wrong, than obviously they failed to take proper precautions to make the test safe), and the show/network could be liable for damages. And for a child, that could mean a lifetime of payments to cover their injuries. To say nothing about the emotional effect on a jury, possibly leading to high punitive damages added on.
Better just to avoid that risk by skipping these kind of tests.
And as people said, nothing blows up to make a good ending!
Even better was the look of bewilderment on their faces, that “WTF?” look as they tried to figure out how NOTHING was taking their candy. Then came, of course, the ultimate weapon in the baby arsenal…guilt.
<snip> I remember getting a big kick out of Scotty making an analogue of the little girl for initial testing; it was a 50-pound sack of sugar onto which she’d painted a face and glued pigtails. <unsnip>
What ever happened to Scotty? Conflict with Kari?
I believe I read that Scotty quit to concentrate on her art, which has something to do with welding pieces of metal together.
Left the show for “personal reasons” after Season 3, though she’s been back on a few times since then (which would suggest it was a reasonably amicable parting). Personally, I wonder if she wasn’t comfortable with the increasingly high visibility the show’s cast was receiving.
As a rule, but this isn’t hard and fast. My girlfriend is 16 years younger than I am, and we tested a range of frequencies the other night. We both dropped off about the same place. I forget the exact Hertz, but neither of us could hear it, even though I had the sensation that my ears hurt.
<snip> testing Monster cables versus wirehangers. <unsnip>
No. Wire. Hangers. EVERRR! Ok, I got that out of my system. 
I imagine even if they convinced parents to hand over their kids for an experiment it would be hard to get the kids to follow directions when there are strangers/tv stars, cameras and explode-y things to distract them.