Right, totally agree, but this is not the reason that micropayments is not more commonplace. It's equally difficult to get people to log into a payment system to pay $1.40 vs $1.55.
I already mentioned two ways around this, which is why your argument is void: Holding small amounts in PayPal (or similar) accounts, and bypassing cards entirely and using bank routing transactions. Both are solved technical problems.
At brick and mortars, where they are operating on 5% margins in many cases, a 3% skim off the top is massive.
A 3% arbitrary fee for every electronic payment in north America is really, really quite a huge thing.
It's quite massive form of rent extraction, given that there is no real IP, and the actual cost is almost nothing.
It's one of the biggest and juiciest forms of obvious oligarchy/monopoly that there is.