I agree, don't despair...kids don't have the heural pathways to be able to predict their movements as it were, until a certain point.
this is documented somewhere in research.
First they recognise when they are wet/have done a poo.
then they notice when they are doing it and the sensation that comes with it.
then later they begin to recognise the sensations that come just before it happens, but not soon enough to be able to control it.
It's only at the last step in development of this process that they actually recognise the wee or poo approaching, and are able to control the muscles for long enough to shout 'I need a weeeee!!!' and dash to the potty, sometimes making it on time, sometimes not.
You can't encourage this process with sweets, it happens by itself.
Using punishment, rewards etc isn't worth doing and can make your child feel bad for something they cannot control.
It happens - mine were at roughly three to three and a decent half before they totally got it, but when it happened there was no going back.
Some kids do it sooner, but this is a totally normal age.
So please don't worry or panic, you're not going to have a nappy dependant adult on your hands.