Remote attestation absolutely provides increased security. Mobile banking fraud rates are substantially lower than desktop/browser banking fraud. Attestation is major reason why.
I think ever compute professional needs to spend at least a year trying to secure a random companies windows network to appreciate how impossible this actually is without hardware based roots of trust like TPMs and HSMs
It's not even that. The main reason is probably that attackers are going to be writing code to automate their attacks, and desktops are easier to develop on than phones, so that's what they use with no reason to do otherwise.
Even if you stopped supporting desktops, then they would just reverse engineer the mobile app instead of the web app and extract the attestation keys from any unpatched model of phone and still run their code on a server, and then it would show up as "mobile fraud" because they're pretending to be a phone instead of a desktop, when in reality it was always a server rather than a phone or a desktop.
And even if attestation actually worked (which it doesn't), that still wouldn't prevent fraud, because it only tries to prove that the person requesting the transfer is using a commercial device. If the user's device is compromised then it doesn't matter if it can pass attestation because the attacker is only running the fake, credential stealing "bank app" on the user's device, not the real bank app. Then they can run the official bank app on an official device and use the stolen credentials to transfer the money. The attestation buys you nothing.
>Attestation is major reason why.
It's not. Mobile applications just don't have unrestricted access to everything in your user directory, attestation have nothing to do with it.