The comment above didn't mention what type of card they are using nor in what country they live. Regarding Windows, in the times of Windows XP there were no "telemetry".

Using a smartphone for banking is really dangerous because banks often use a phone as a second factor and compromising the phone gives full access to your bank account. And many phones do not get security updates.

I'm not referring to Windows as poor for telemetry, but it's tremendously easier to get malware that takes over your whole system on Windows than any other platform - consider the fact that downloading and running unsigned executables is an extremely common practice - even as a fairly security conscious person I do it regularly on Windows. Add to that the fact that Windows completely lacks sandboxing and you pretty much get a pile of malware on your machine unless you really know what you're doing - and even then I've seen fairly technical people click next past a "bonus ask.com toolbar" in an installer.

Even with a regular bank account in most of the world at least, it's tightly regulated and you're only liable for a small portion of the loss - on a credit card, generally nothing at all.

Even without OS security updates, generally browsers and other internet connected software gets security updates regularly, I'd trust a new user on Android far more than Windows because clicking an ad would not have a risk of getting them infected system wide without jumping through some serious hoops and involving a few exploits. On Windows that's one Run button press away.