For most online marketplaces protecting the buyers at the expense of the sellers may be necessary. There are usually a lot of buyers, they are reluctant about buying things they cannot see or touch from people they don't know, and most are not in a position to absorb the fraud. Meanwhile the sellers are usually companies that can absorb some reasonable amount of fraud because they can spread the cost of the fraud over the much larger number of transactions.

That's not always the case, such as in situations where individuals are trying to occasionally sell items of value and they are not in a position to absorb the fraud. For those situations it may make sense to use an escrow mechanism, because non-reversible payment methods like Bitcoin may spook the buyers (and insufficient buyers may lower the overall prices, potentially beyond the cost of escrow).

None of this requires anonymous payments.

The EU can still suck taxes from the transactions of Taler but at least they have no idea what you bought. Why should the payment middleman have a complete itemized dossier of your personal purchasing history just you and the merchant should share the details of the purchase beyond the total amount paid.

Because the government has a legitimate interest in taxing different goods at different rates.