They are Registered Envelopes. The registration labels indicate they are from philatelic bureaus. They most likely had new issues in them.
Destroy is a strong word, but to postal history collectors (stamps on the envelopes) removing the stamp from the original article is in fact destroying/ruining the article.
There'll be no place in the stamp album for them but there are plenty of options for the storage of covers/envelopes.
The Bermuda cover is quite attractive, to my eyes anyway.
Hope this helps
