Because it's not a good argument. The fees are low because usage is low, but as soon as usage rises, the fees will rise again too. That's a broken system. Also, fees on BTC today are still not negligible. Average is 30-50 cents USD, which is unacceptable still for many parts of the world. BCH fees are 0.2 cents.
This is where that whole "blocksize debate" turns out to have been worth discussing.
A sudden increase in demand for BTC will send the fees through the roof because of it's tiny 1mb blocksize. The same increase in demand will result in ~ 1/32 the increase in fees. This is due to BCH's 32mb block size.
