Implanted cyberware always comes with the necessary neural interfaces so the user can make it work without requiring anything else. Nevertheless, legally manufactured cyberware makes heavy use of wireless Matrix networking, for a number of reasons:
The most important, however, is for communication between and coordination across different cyberware subsystems. It is quite difficult to run enough cables through squishy flesh to hook up everything to everything else. Plus, different pieces of cyberware from different manufacturers run on a mishmash of semi-incompatible low-level protocols, and that stuff is hard to change when it requires surgery to get at the controls. Instead, commercially available cyberware usually just uses the wireless Matrix as a sort of universal communication bus.
Consider a high-threat response soldier fitted with a smartgun system, cybereyes, and a cyberarm with recoil-compensating gyroscopes. When they fire their weapon, all these systems need to work together in harmony to compute trajectories, display the results of this computation to the user via an ARO, key up the gyros to make just the right motions to counteract the gun’s recoil as they fire, and so on.
To do all this without the wireless Matrix requires a lot of wires criss-crossing the user’s body plus a coordinating processor to mediate the different protocols used internally on each piece of cyberware. These devices exist - they are called internal routers - but they are invasive and expensive and offer limited benefits to legal users. Most people just rely on their devices’ ability to use the standardised protocols of the wireless Matrix to talk to each other.
Besides, the corps like it that way. Most corp security guards are under-trained, under-paid, over-worked, and over-dosed on (at least) stimulants and (quite possibly, at the first sign of trouble) combat drugs. The corps know they can’t be trusted not to wipe each other out in a hail of blue-on-blue gunfire. But proper training costs money, money that goes down the drain when the next shadowrunner team deletes Jimmy; and if there’s one thing the corps hate to do, it’s spend money.
The answer is ubiquitous wireless. Logging of patrol routes so you can be sure they’re not shirking. Inventory tracking of each and every valuable and dangerous item via RFID tags - right down to the bullets in Jimmy’s gun. Remote biometric monitoring, so you know if Jimmy gets jumped, knocked out, or flatlined by intruders. Smartgun fire systems with biometric triggers and linked to friend-or-foe tracking, so the bad guy’s can’t take Jimmy’s gun from him, and so Jimmy can’t get trigger happy and accidentally splatter your star researcher’s expensive brains everywhere.
This isn’t always the case, of course. Elite troopers, from HTR squads on up, are fully trained and perfectly capable of working as a team without the crutch of a wireless network (if they are willing to forgo the benefits of realtime heads-up tactical displays). But Jimmy? Honestly, if you took his wireless away, he’d be a straight-up liability to himself and others. With all this wireless gunk, you barely need the human being to think at all, and that’s the way the corps prefer it.