A few reasons are, due to their size and open design, they tend to be susceptible to marks; they weren't as readily collected IN MINT STATE initially and the mint sets issued were problematic, as far as storage devices go.
Several reason, some of which are mentioned above. Here are probably the top three reasons:
(1) The relatively open design and large size of the coin lead to a susceptability to bagmarks. Look through some original rolls and you'll see what I mean.
(2) The strike quality of many dates was poor (particualrly the '53-S and dates in the 60's). Look through some original rolls and you'll see what I mean.
(3) Most, perhaps all of the 67s are toned to some extent, and probably came from mint sets (and yes, there are a few exceptions, such as the '50 P in 67FBL). While there are/were many nicely toned mint set examples out there, that have/will/would have made 67, many have been dipped (may be dipped in the future), and now won't make the 67 criteria.
Comments
Many that were put away, now have problems do to storage.
I also feel we can blame Lucy for the shortage
(1) The relatively open design and large size of the coin lead to a susceptability to bagmarks. Look through some original rolls and you'll see what I mean.
(2) The strike quality of many dates was poor (particualrly the '53-S and dates in the 60's). Look through some original rolls and you'll see what I mean.
(3) Most, perhaps all of the 67s are toned to some extent, and probably came from mint sets (and yes, there are a few exceptions, such as the '50 P in 67FBL). While there are/were many nicely toned mint set examples out there, that have/will/would have made 67, many have been dipped (may be dipped in the future