They are, and frankly that they need to exist is the single most egregious example of why USB isn't what I need it to be. What (I'm surprised) I haven't seen is a male-to-female adapter with a switch on it that physically kills the data tx lines.
You'll note that many chargers started dropping handshaking because it was inconvenient. To be compatible with anything you need it, but there's many that don't ask, though they may only work with the equipment they were sold with. (E.g. defaults to 5V 2A charging.)
The historical design intent of USB is that, even when your laptop is in standby it still powers devices like your keyboard (so you can press keys to wake it up) and in exchange, devices promise to consume less than 2.5 milliamps (12.5 milliwatts) until they've negotiated permission to draw more from the host. After all, it'd suck if your laptop battery was going down noticeably even when the laptop was in standby.
Of course, loads of vendors of cheap devices ignore this - the makers of a $5 rechargeable bike light or USB fan aren't going to put in the components needed to negotiate charging speed. But in principle if you made a USB cable with only the power pins connected, compliant devices should only charge exceptionally slowly, if at all.
(Wall chargers, instead of enumerating as a USB host to negotiate power, used to put a certain value of resistor across the data lines, to signal what current the device could draw - this hasn't always been standardised, which is why phones and USB chargers can be incompatible)
Note also a fair number of laptops (read: every one I have used and checked) use PS/2 internally because it is interrupt driven and even lower power than USB. There are also plenty of laptops that advertise high current phone charging while off, some of which do negotiation, some of which don't.
[0] http://msdn.microsoft.com/en-us/library/windows/hardware/hh8...
Ignoring that, I'm not sure it's an improvement. Most of the power savings is having the keyboard initiate an interruptible event to wake the computer. Interpreting HID like in USB means the keyboard can't wake the computer, the computer needs to remain on to service USB interrupt endpoints.
The laptop I had with an always-on charging port actually charged things faster in standby, because that turned off the negotiation.
> defaults to 5V 2A charging
i don't think you understand how power transfer works.
voltage is applied (by the charger), and current is drawn (by the device that wants to charge). a charger cannot "dump power into" anything.
when chargers and devices attached to them engage in some sort of negotiation, that's not the device telling the charger what to do, that's the charger telling the device what its limitations are.
if you attempt to draw 3A from a device that can only do 2A, the voltage will drop outside of the specified range. to the extent that a charger can limit the charging current, it does so by dropping/cutting off the voltage until the current goes down. which isn't ideal for devices.
(perhaps you're confused by thinking that USB "chargers" are like battery chargers, and arbitrary USB devices somehow act like batteries. that's all wildly wrong.)
The main concern behind negotiation seems to be safety of the user and safety of the power supply. Detecting a safe load means detecting a not-short.
The basis for the 5V power negotiation on USB is extremely silly. The power supply is already current limited, protecting you from shorts, and the supply voltage is ~5V, quite far from anything dangerous.
This may be true for wall chargers but not devices capable of supplying power to peripherals while on battery power themselves.
For example, an external hard drive should not have to figure out that a large tablet can power it, while a phone won't, though trial and error, by attempting to spin up the disks multiple times.
Devices are going to misbehave anyway, it's probably more important to default to a reasonable level of mostly works.
Less generally, these batteries can also break ground loops, which comes in handy when connecting a power supply to both a USB device and an attached analog audio device (e.g., iPhone and wired noise-canceling earbuds).
Android already allows you to only use an USB connection for charging. Setting this as the default when you are in an unknown place sounds reasonable.
OTOH, a USB Y-cable physically has no data lines connected on the extra USB-A male connector; it thus provides a far stronger guarantee that there is no data travelling across them. (Not foolproof, but safer than a software-controlled switch.)
If you don't trust that cellphone won't transfer your private data via USB, I don't understand why you trust it not to do it via any wireless connection.