Another advantage with ew ratio betting for 'percentage of pocket' punters is that they can usually afford to bet larger amounts per bet. If a punter only has say $100 in their pocket betting money for a Sat. of punting, it is very unlikely that punter will have $20 win bets. 5 'outs' and their finished, so the punter would probably be having $10 win bets [or even $5 bets, if they like a lot of action].

A punter is more likely to risk [say] $3x18 ew bets than $20 win bets because the potential SR for a return is a lot higher with the former. That is probably the reason straight ew bets are still so popular, even though they are a very bad bet [50/50% ew] When a horse places, which mostly is what happens, there is no profit and often a loss [place paying less than $2], but there is a better SR for this bet than a straight win bet and that is all that seems to matter.
The fact that their is usually no profit either when a straight ew bet places, seems to slip their minds. They are basically waiting on a win to make any profit from a bet. They may as well have straight win bets for half the cost of the 50/50% ew bet [they would get twice as many bets for starters]. It's the lower SR for the straight win bet they don't like. Logic [or maths] doesn't get a look in, because for a straight ew bet there isn't any !

Realistically, $3 x $18 ew [for convenience, $5 X 25, $5X20 or even $5X15] bets for most punters gives them a significantly better chance of being in front at the end of day than straight win bets or 50/50% ew bets. If their average win SR for 50/50% ew bets was high enough to turn a profit [very doubtful], it's high enough to have straight out win bets for a far better result.