We don't see skinlink or DNI cables tech b/c they don't want that avenue of attack closed. You want the good bonuses you gotta have the tech and the role to keep your sh*t from getting bricked.
Cyberdecks and data-
jacks come with a meter of built-in retractable microfila-
ment data cable, or you can always buy a cable for about
five nuyen per meter (some devices, especially those in-
stalled in buildings, are connected by cables to mitigate
noise)
DNI cables very much exist. Skinlink doesn't yet, but I expect to see it show up at some point.
As regards other points brought up in this thread:
Many of those good bonuses are *Wireless* bonuses, not DNI bonuses. The presumption is that DNI enters into it at some point (because pulling your commlink out of your pocket to interact with it in order to eject a clip seems like a more involved task then just ejecting it normally), but whether you are directly connected via cable, or connected by wireless, the feature is categorized as a wireless function. So, yeah, you could connect to it by wire, but you'd still (for some reason) have to have the wireless turned on in order to get the wireless benefit (such as the action economy stuff that was obviously intended to only require a DNI).
Important to remember - DNI =/= Direct Connection. DC requires a wire (data taps being a potential exception, but the wording is unclear, which is an entirely different conversation), DNI doesn't.
A GM could house rule some "wireless" functionality to still work without requiring matrix connectivity - just some means to connect to your DNI. This would include things like the tripod's ability to fold up, deploy, or detach as a free action (since this is really just sending a mental command to the device), but not things such as the Smartgun system's dice pool bonus (which requires matrix access to make use of external resources). The rules conflate the two in order to, like you mention, give hackers something to do, even though many don't make sense.
Wireless is handier than running cables to everything (especially since the concept of a switch seems to have vanished from the world thus requiring you to have a datajack or trode set for each device you'd want to connect to wirelessly), which is probably why they wrote the rules in such a way that they assume that your DNI is wireless enabled, but if you opt to connect to things by wire, they end up looking very odd.