If the "Hey, Siri" feature has been setup and turned on on your phone, you might want to go to Settings > TouchID and Passcode > Allow Access When Locked > and consider changing the default (all enabled) settings.
If you happen to put your phone down somewhere and forget about it, or if your iPhone gets stolen or ends up being passed around at a party or family gathering, you don't necessarily want everyone being able to find out where your car is parked, who you last called, where you live and other personal information etc.
If you happen to put your phone down somewhere and forget about it, or if your iPhone gets stolen or ends up being passed around at a party or family gathering, you don't necessarily want everyone being able to find out where your car is parked, who you last called, where you live and other personal information etc.