A simple transaction cost of maybe 1cent per share wouldn't affect a normal buyer at all,
Oh, yes it would. Say I'm a small trader with a small account of $10,000. No margin. I'm trading stocks under $2.00, and I buy 1000-2000 shares at a time (that's $2000-$4000 per position). I get charged $8 to buy or sell, so that's $16 in fees for one round-trip (buy and sell) trade.
Adding a $0.01 fee PER SHARE (not per transaction) adds in a $10 (1000x0.01) to $20 (2000x0.01) fee, so that's $20-$40 in extra fees per trade, plus the $16 per trade = $36-$56 just for ONE round-trip trade.
With fees like that, I might as well telephone in each trade to a broker and hand them the fees, and give up on individual trading altogether. I'd have to make that up in higher and higher profit for every trade that I make. Sometimes I'm only making $50 gross on a trade, and $34 net profit after the broker fees. That's not a lot.