WRZT691

We’re all capable of making comments that are baffling in retrospect. Don’t beat yourself up about it. You seem like an honest and humble person which is much more important than being a smart-ass. 

In this screen grab, we can see the end of an FCC-initiated high-speed pursuit that was the result of a perpetrator transmitting on a Wouxun KG-XS20G on channel 8. The FCC handed the chase over to the highway patrol when they realized they had no vehicles with which to chase anyone. 

GMRS mobiles radios only go down to 5 watts so they aren't allowed on channels 8-14. That being said, I do know of at least one mobile radio that will transmit on those channels. Not like I would do that though. 😇

I feel the urge to ... no, never mind

Pursuant to Section 95.1767.(c) the power on the 467 Interstitial freqs are regulated to half a watt ERP. 

Groups and families within a close range of each other use these channels to avoid clutter and interference from others using these Channels.

The one mobile radio that I know will transmit on channels 8-14 is a type accepted GMRS mobile radio. The Wouxun KG-XS20G definitely will transmit on channels 8-14 if you set them to low power (5 watts) and also set them to narrow band.

Type-accepted GMRS mobiles don't transmit on those channels because they aren't allowed to:
467 MHz interstitial channels. Only hand-held portable units may transmit on these 7 channels. The channel center frequencies are: 467.5625, 467.5875, 467.6125, 467.6375, 467.6625, 467.6875, and 467.7125 MHz.
Note that it says "hand-help portable" only.  Nothing to do with power limits.  Probably more a case of "mobile GMRS radios don't go down to .5W because there is no point" rather than "can't transmit there because the minimum power is too high".
I'm sure you wouldn't transmit there from a (non type-accepted) mobile, because you dont' want to take a chance of interfering with a repeater on an adjacent frequency.

As far as I can tell, for GMRS, those channels are only useful for radios like the Baofeng MP31 that can transmit at .5 watts on those channels.
RF Output Power ≤2W (1-7&15-22&23-38Channels) /≤0.5W(8-14Channels)

The FCC screwed up when they allowed the sale of combination FRS/GMRS radios before the rule changes in 2017. The idea was if one wanted to use the GMRS specific, at the time, channels one would have to get a GMRS license. Well, almost nobody bothered. So, when the rules were changed in 2017 the FCC had to do something about all the existing radios out there. They simply changed the rules to make those combination FRS/GMRS radios FRS only and legal to use as is.
However the channels you pointed out sit between the main GMRS repeater input channels, which use a 25KHz channel. The FRS channels, 8-14, where kept at very low power and narrow band since they partially overlap the main GMRS repeater channels. The idea was to minimize the interference they cause. At the time FRS was limited to 0.5 watts and narrow band, 12.5KHz channel, so keeping the restrictions didn't require any changes to existing radios.
As you pointed out for FM use they are basically useless. Many GMRS specific radios don't even include them, noticeably on mobile radios. So practically speaking GMRS really has useful access to only 15 channels. 
You might ask is there something that those channels could be used for? Maybe, but that's a topic for another thread, which if you look you'll find on the forum discussing adding channels to GMRS. 
FRS-GMRS Channels Layout.pdf

So the converse: if you are operating an FRS radio on one of those channels, or any other FRS channel, you do not need to ID.

Short answer its to allow full compatibility with frs. Those channels were originally FRS only pre 2017.
Yes if operating a gmrs radio you need to by rule announce the same as any other channel.
 
Those channels if you look at frequencies are close to repeater inputs and the reason why power is low is to prevent any interference on the repeater inputs.