Or it could be that some people don't want to attract attention to their paper wallets... plastering Bitcoin logos all over it confirms exactly what it is and may just catch the eye of someone leafing through a stack of papers on your desk.
Whereas, a "plain" sheet of paper might go unnoticed.
There are a couple of nice ones here:
https://bitcoinpaperwallet.com/bitcoinpaperwallet/generate-wallet.html#And they have a template... Personally, I quite like the "Hobbitcoin" one