I think PP what you are actually describing is peoples' ignorance when it comes to configuring the most basic windoze security.
M$ ship the product wide open. Just like most wifi routers are shipped (and thus installed, by "ignorant" users) wide open.
Setting up wpa/psk on the router, and a few other bits like blocking the admin port, and setting a login/pwd on the windoze machine and disabling "simple file sharing" makes a pretty secure setup.
Whereas "unix" tends to be used by serious geeks and nerds
who know a lot more about this stuff to start with.
As regards internet banking, the absolute #1 requirement is physical security of the machine. If you let kids (or careless adults going to odd websites) play on it, it will be loaded with trojans within days if not hours.