I was wondering why some (Visa) cards are issued as Signature and some as Platinum.  Is there some advantage to the bank for example not to have signature.  Looking at my Visas in order of decreasing CL (highest is 30K, lowest is 15K)

Capital One No Hassle, platinum,

Chase Amazon,  Signature,

Penfed, Platinum

Capital One Plat, platinum

Citi AA Visa,, Signature

US Bank Cash Plus, Signature

So it doesn't seem related to CL or when I got the card (Penfed and US Bank in the last two weeks for example).  And also not just the issuer, as Cap One does have signature cards as well.  (Although it looks like Penfed doesn't).

Any ideas?