Siri and Wallet from the lock screen are incredibly convenient—but they're not secure!
Apple's voice assistant, Siri, can provide information and execute commands even from the lock screen. With the iPhones 6s, it can even be activated by your voice alone. That's incredibly convenient, but it also means other people can ask Siri for some basic types of information as well, and that's not very private. For most people it won't matter. The convenience will be more important and the potential information and access exposed not a huge problem. But, if you need to be extra private and extra secure, you can disable Siri—and even Wallet—and force an unlock to access them.