Trying to realistically break into megacorps' networks can be a nice palate cleanser occasionally but it isn't nearly as gamable.I think it depends on what it is. There's stuff (like utilities) that are on the general internet that probably shouldn't be. So, wireless jacking could assume public/general access, not secure/proprietary. And its easier to secure a physical connection access.
So, if you're going after smaller gigs, might not be a big thing. Going after a big target? Its probably safe to assume that at least some things will be wired, depending on how important it is.
"Hi, this is the CEO. I forgot my password, can you reset it?"
Or how about leaving a bunch of USB sticks outside of a sensitive location? That was a big enough problem that the US military had to solve it by using hot glue guns on all the usb ports for their computers.