I never used a passcode on any of my previous iPhones, however, with the 5S I use the Touch ID.
Worked very poorly when I first got the phone, but after the 7.1 update it works great.
I have a lot of personal stuff on both of my devices. I assume that one day I will either lose or my devices will be stolen. Its prudent to have a passcode. Like one commenter said, who doesn't use the fingerprint ID or a passcode. Its stupid not too.
Prior to me getting my 5S, I never had my previous iPhone's passcode lock enabled. However, since I have my phone with me everywhere, I utilize Touch ID. My rMini, however, does not have a passcode lock on it since rarely leaves my place.