Keep in mind these are the restrictions for the entire archive. Here, on the other hand, are the policies just for the LoC Rare Book & Specialized Collection Reading Room:
The National Archives is similar, as well as NYC's archives downtown. I've been in both and have easily handled old-but-not-so-old (1800s) volumes. Putting that kind of restriction on the entire archives throws the baby out with the bathwater.
http://www.loc.gov/rr/rarebook/policies.html
tl;dr I can walk in and look at some rare books.
The National Archives is similar, as well as NYC's archives downtown. I've been in both and have easily handled old-but-not-so-old (1800s) volumes. Putting that kind of restriction on the entire archives throws the baby out with the bathwater.