I don't think people would be so averse to laying chalk if it wasn't so ingrained in the US bettor's consciousness to lay to win a unit, rather than to lay a unit.
just my opinion,
much greater room for error consistently betting dogs, IOW in the 90% example above, there is only from 90%-100% chance to win, if I bet on something I perceive to have a 10% chance of winning, my guess can be way off, as we get the entire from 10% -100% to be correct.