For supported rides, there is no need for the extra water storage but to each her own. I don't like the weight on my bike and the added heat. Harder to take off and put on layers, and get to my snacks while riding.
Somehow I've never felt they were safer but then I can't get the hose to be in just the right position without leaking or hitting me in the face or flopping around distractingly. I have to unclip and re-clipping the hose means I have to look at it, unlike a bottle. Not to mention, after you've snagged a jersey with the velcro sternum strap you keep them relegated to mtbiking with jerseys that you know will be a risk anyway.
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.