You realize you're asking a rhetorical question right?
The liquids ban is a stupid rule to begin with, and you're asking the TSA to make a common sensical rule on the size of tiny bottles of liquids allowed?
Here are some more rhetorical question - why do I have to take my flip-flops off when walking through the WTMD? Why is that so deadly dangerous?
Why do I have to show my boarding pass to the ID checker (revenue protector) 10 feet from the WTMD, and then have to show it again at the WTMD? Are there some concerns a terrorist will be able to slip between the 10 feet from the ID checker and the WTMD??
You might as well go ask a dog why the sky is blue. At least the dog will answer honestly - that it won't be able to answer at all.
So what's the answer to your rhetorical question? The answer is - the TSA = utter lack of common sense.