First of all you are way over generalizing here anyway, since not everyone pays the highest tax bracket. Also, a serious trader might trade inside a corporation with deferred taxation by an individual until withdrawn, and only withdraw marginal amounts enough to live on and tax treatment is different yet again than individual taxation on all gains when trading under their own name in nonregistered retail account. So money can continue to maximize market gains. I think most traders consider taxation being a factor but being taxation, there are too many scenarios to make blanket statements.
Volatility presents trading opportunities. In a defined bull market with no volatility, buy and hold wins. In a bull market with lots of volatility trading in channels, trading makes more money provided someone sells short term peaks and buys back at short term bottoms lower than their sell price. Perhaps gains enough to overcome frictional losses of taxes, as I presented in my earlier example.
And like the other guy said, most traders trade because they want to way out beat the market and achieve out sized gains, not something that only beats the market by 1%. Take this year. The S&P is flat to negative now for the year. Pretty much any trader who traded this year with a profit made more than any buy and holder.
But you ultimately agree with my original point. Theres no broad stroking generalization here. You might as well compare S&P buy and holders vs failed traders who are down a lot this year as evidence that buy and hold is the better method. A trader can achieve gains that make it worth while even after taxes. Traders may also value capital preservation and their in and out of positions affords them the ability to choose when to risk capital. Someone who does buy and hold and never looks at it again, might be sitting on losses for a few years. E.g. S&P buy in @ 2007 breakeven was 2013. Citigroup buy in 2006, down +80% in 2014.
Finally, someone who is a career trader as their only breadwinner will need to draw down from cash. Someone sitting on a huge paper gain on non-dividend payers can't pay the bills.
A lot of straw man arguments here.
You cannot deny that the taxiation of short term gains vs long term gains makes the hurdle rate for trading short term higher than that of long term. You cannot deny that the higher the hurdle rate the harder it is to succeed at something.