The reason for taxing children has little to with revenue, and is mostly there to keep thr code simple and people honest.

In your scenario, every moderately wealthy person would start doing stuff like create an S-corp, hire their kids on to fake jobs, and then take the money back from their kids plus declare the wages as a net loss to wipe out their own income taxes.

If teenagers aren't being taxed, then they are effectively getting higher wages than adults. Lots of people have the "crab pot" mentality in that anyone getting more than them means they are getting less. That alone would negatively affect workplace environments. Then also businesses will have a perverse incentive to higher more teenagers at potentially lower costs to them, which keeps them out of school or training for any other type of work. It's also likely that some businesses will be dishonest and keep income tax witholdings for these people themselves, or pay them as well as older employees on 1099 effectively cutting real wages.

There is easily enough problems with changing the tax code to completely remove a segment of the population that could have lasting damaging effects on everyone. In general, many under 18s are already shirking their tax obligations with under the counter gig jobs and the lower total amounts they earn typically puts them at owing little to nothing anyway. Your opinion, while valid, is neither practical or necessary to implement.