It also helps when they get a bit older as well I think. A bit like how when you train them with potty training and give them treats to go in the right place, well once it becomes second nature and they just do it they don't require all the treats anymore (I still tell mine they are good though!) Treats help when you are teaching something brand new and they help to reinforce what you are trying to get accross but once they get older and these things are routine I think praise and a happy voice works just aswell for them

I've moved on to mainly cuddles and praise, but periodically I do 'treat training' just for reinforcement.