Bubbles are a great early lesson in cause and effect (that one event makes another event happen).
Babies demonstrate this from a very young age as they begin to realise that when they put their fingers out to catch a bubble it often pops.
The brain has a lot to do with this purposeful action as it coordinates the eyes and hands to work together to achieve this desired outcome.
As your child grows they begin to develop foresight and will learn that their touch will pop the bubble.
Then when they learn how to blow bubbles themselves, their brain will provide real-time problem-solving abilities by informing them to adjust their breath, hand position and how much mixture they need to put onto the stick in order to achieve the desired outcome.
Pretty amazing how much is going on behind such a simple activity.