I could not have said it any better!
The label resource does not discriminate by price. Value priced vintage garments (not what they go for today, but how they were marketed back in the day) are included. JC Penney brands, etc, are there. (but of course the clothing that was more "value priced" back then would probably have better construction than now).
Like Lizzie touched upon, It is just that some of the more couture lines do have a high collector following, so people have written books, etc, about the particular designer and lots of information is available.
Information on smaller department store lines of clothing - especially because they were not kept track of like the design houses, were sometimes lost. some were higher end and exclusive, but many were more value priced. The in store brands, etc, that were available were bought, worn every day and worn out so not as many examples survive. This would be like the Sag Harbors, and the St. John's Bay, and Kathy Irelands of yesterday...they were day in day out clothes for many people, and people didn't think to save them or ponder their origins like their wedding gowns etc.. Heck, i have some t-shirts my sister sent me that i wear everyday and i could not tell you what the label was.
Just reading the label resource has made me really more aware to pay attention to such things when things are new...
I LOVE Lizzie's Mystery labels thread, because you never know who might recognize a label. It might have been a small brand in a part of the country where they lived back then and the information would finally come to light!
Chris