Why have the control go through a sophisticated programmable chip and not just use a simple transistor/relay directly connected to the sensor?

A “simple” transistor or relay is bulky and expensive. By comparison, routing through a programmable chip (which is already on the board) is nothing more than routing work—it doesn’t add anything to the BOM.

This is just the way people design circuits these days, because it’s easier and cheaper. A single µC with a few GPIOs, rather than a bunch of logic chips scattered around the board.

Even on programmable chips, not every part of the chip is programmable.

The goal is to make this so it cannot be overridden in software. By designing hard-coded logic in a chip that already exists, you can get the same level of security for essentially zero cost.

Especially, even if this is programmable, this chip is probably not programmable from the point of view of the motherboard...

And if an attacker is able to connect a chip programmer on your motherboard, you have a totally different threat model and bigger problems to worry about.

because it already has to go through it for signals processing

Why should it go through yet another redundant mechanism.

Have you ever seen a MacBook from the last 10 years? There are no physical switches, it's an hall sensor that works with the magnets that keep the thing closed.

Physical switch could be made INSIDE the laptop and would be automatically pressed by the lid itself - when the lid is closed. No sensors needed. No chip needed. When lid is closed - mic is disconnected. When opened - mic is connected... User does not need to do anything else then closing the lid...

There are people out there that hook up their laptop to an external display and then use it with the lid closed. Wouldn't be surprised if some of them want to use the mic with that configuration as well.

Then they are out of luck with this new T4 security chip cutoff, Apple says that it cuts off the mic when the laptop is closed, and there's no way even the kernel can override it:

“This disconnect is implemented in hardware alone, and therefore prevents any software, even with root or kernel privileges in macOS, and even the software on the T2 chip, from engaging the microphone when the lid is closed,” said the support guide.

So in this respect, there's no difference between the T2 chip cutoff and a physical switch... except that there could still be a backdoor in the T2 chip cutoff that Apple hasn't admitted to.

In my experience, it doesn't work very well with the lid-closed... therefore I (like many of my colleagues) tend to use external mics, too.

It's a shame. It's a damn fine third or fourth screen (I'm writing this on it).

I dock because I only like one screen. My workflow is already optimized for my laptop screen (I'm on it 60% of the time). So my ideal setup is one massive screen when I have the choice.

I could credentialize in multimonitor usage (I have before), but now I'm getting used to something that's incompatible with portability.

Physical switch could be done with a very small magnet behind the lid surface and an opposed micro-reed switch (or other magnetically actuated on/off device) buried behind the body surface. No surface penetrations, no exposed moving parts (reed relays are hermetically sealed).

Reed switches are pretty damned huge when working at the scale of a laptop.

Not to mention it would make the case of the computer microphonic — bump it hard enough and that’ll be transmitted through the reed relay.

Yeah, I agree. Reed switches might even resonate with music played through laptop speakers. This needs a no-moving-parts magnetic sensor.

And a magnetic switch is far too easily defeated

My parent’s table pads do precisely that. After a particularly baffling family tech support call I drove over. Their kitchen table pads magnetically lock to stay nicely aligned, and also either put a laptop to sleep, or keep it awake when closed depending how you place them.

How? The point is to prevent invisible eavesdropping not prevent some spook on the table from hacking you.

too easy to fix if it breaks

A switch is more likely to break than a sensor and there’s already one for closed lid.

theres just no lolz round here