I don't know, some very good growth funds may have turnover rates that easily can exceed 200-250% as a turnover rate. I've seen some with 600-800%, and granted, no one should be stupid enough to have their entire portfolio allocated to a high turnover growth fund, but still...(low cost index funds are still great for a lot of newbie investors btw) A person with say 1,000 invested in a 250 percent turnover investment vehicle is paying $25 year after year and compounded it would add up in their retirement. Ok sure, it's just $25 but 2.5% of your investment being taken out is not chump change for some people and I would object to this $25 just as much as I would a $25 extra fee for someone making under 20k a year as a low income person if it isn't necessary. It's so easy to say for example what's an extra 20 dollars for a struggling person paying just a tad more on their income tax, but 20 dollars is still something important to somebody with a real need.
I don't think you should create disincentives for people to try and save for retirement when it is incredibly simple to create a sliding scale that either 1) slightly minimizes the overall revenue being raised by creating say valuation and/or a small trade limit per year exemption (to in theory allow people to save their assets if the markets tanks, etc) or 2) slightly tweak the numbers to target specific types of trading (frequency and volume) that actually would work better, help deter the wild speculative trading that created already at least one macro financial crisis, and likely raise more money. The objections of the rich and powerful in all three of these scenarios would not really be all that different anyway, as they will attack any proposal of this nature. The odds of what I am proposing as an alternative possibility would not be all that different (in terms of having a chance to actually pass as a real law in America) than what is being proposed now, and it's definitely much better optics as a champion against Wall Street and being for the little guy, etc.