I don't actually have a Snapchat, but my friends and I have lately been discussing the emergence of the "Snapmap," which basically allows friends who have added each other to literally see exactly where the other is through GPS.
I find this unsafe, and thankfully there's an option to turn it off, but my friends claim the default setting is on; many users will unknowingly reveal their locations at all times. Kinda creepy, eh?
You're right, others have done this (Apple's Find my Friends, Facebook's Live Location, etc.) begging the question as to why people panic over this one. After doing some digging, I'd say it's because the app automatically activates it after an update.
To be fair, users are given a walkthrough and a chance to activate "Ghost Mode," somewhat mitigating the issue. Nonetheless, even with a tutorial, I'd advise caution for SnapMap and other forms of location sharing.