Why Is There Duplicity In Scott National US Albums?

Hi,
I collect US stamps from the beginning thru 1999, utilizing a couple of Scott National Albums. There are two areas of duplicate entries that I question. The first is with coil stamps, where single issues are included, and then the same stamps in pairs are included (i.e. transportation issues).
The second instance is where individual spaces are included for state flowers, birds, animals, etc. - as well as a page for a full sheet of the same stamps.
Why does this exist? To sell more stamps, better presentation, ???
I'm really not complaining, just wondering..............
Thanks,
Mobilman44

Collectors collect se-tenants and coils in several ways. For coils, it is common practice to collect coils as two - coil pairs ... and if for a plate number, many collect as a strip of three with the plate number on the middle stamp! Some collectors would rather collect a coil as a single stamp.
The same holds true for se-tenants. Many collectors collect the individual stamps whereas other will only include attached se-tenant stamps.
The album pages are there to provide space regardless of how you collect those particular issues. For pages you don't use, save them in a file.

There are likely many reasons is Scott's after all. But for the single collector I find that dealers don't always have the setent mint sheets singles separated. They are reluctant to break up a mint sheet, so a mint sheet in those cases will satisfy the singles collector and so they are included. Coil Pairs in singles album makes no sense to me at all and should be available separately if the collector wishes to pursue that line of collecting!