What's wrong with drinking plain water?

The number of women (and men too, I'm sure, although I've mostly seen only women) who give their babies, toddlers and young 'uns fruit juice or cola or soda to drink when they're thirsty is quite, quite amazing. Why they don't just carry bottles of water for them beats me. It's cheap, it's good for you, it's easily available and safe to drink straight from the tap in this country... so, what's wrong with drinking water that's just - you know, water? Not flavoured, sugared, coloured, fizzy or any other variation. I can't help feeling that these people are simply, unnecessarily setting up their children to have lifelong bad habits when it comes to hydration.