Software is always in development.
Sometimes there are things to fix, sometimes Apple or Microsoft change something important, and naturally we're always thinking of new stuff.
So we often release new versions, sometimes these are small and free, sometimes they are bigger and chargeable. You can ensure you always have the latest version, even if others have to pay, by taking advantage of the Lifetime Upgrades service.
When updates become available, you will get those first , and at no further cost.