Why does the AKC have a "Terrier group" but not list all Terriers in it?

Maybe some were more of a "toy" type of dog and never used as a working terrier dog.
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Because they're toys because of their size. Tibetan terriers aren't in the terrier group either because they aren't terriers, they were just named terriers.
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Cause they are not true terriers. Thy have been bred to be companion dogs,not to actually work. Yes they have the tenacity of the terriers but they are more of the companion. The standard manchester is in the terrier group its the toy thats not. It is also because of their size.

Boston terriers and Tibetan terriers are in the non-sporting group cause they are not real terriers they are just named terrier cause of there attitudes.

Edit- Lol you dont know your sizes a skye terrier is way bigger then a silky

The silky is lightly built thats why. A skye is more heavier built. Yes they are the same size in height but in proportion and weight the skye is bigger
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Good question - and they refuse to list dachshunds separately - the minis are in the same group as the standards, that's been contested for years.
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Terriers are energetic, with low tolerance and aren't too social. They are small to medium sized, and their ancestors were bred to hunt and kill vermin. The unlisted "terriers" do not fit into this category.
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http://www.akc.org/

The Manchester Terrier is in the Terrier group, it's only the smaller version which is in the Toy group. In the UK (the country of origin) only one size is accepted, but they also have the English Toy Terrier in the Toy Group.
Boston Terriers aren't classed as Terriers either because they were bred as companions rather than primarily Terriers.
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