The short answer is: we are building a product with many benefits for users instead of just an application that can store some bytes of data and sync it between computers.
Now let me explain.
Sync is just one of the benefits of using Snippets. If we had chosen Dropbox or iCloud for sync we would be in the following situation:
- We would need to sell an app to be able to support further development, because we would have no other way to make money from it. Instead we can give an app for free, have more people using it and make money by charging for the advanced premium features.
- There are many features that will not be possible when using Dropbox or iCloud for sync. For example, web application, private and public sharing, changes history, access level management, search by publicly shared snippets, open repository of snippets and some other ideas that we don't want to share yet.
- iCloud is available only for applications that are distributed via Mac App Store. This may be another subject for a discussion, however, Snippets won't be MAC-only.
- Obviously, iCloud is not available on Windows.
- I still have doubts about Apple's ability to build viable universal sync service. They failed with such products in the past and they did it multiple times, it's extremely hard to implement universal sync service.
- iCloud as well as Dropbox was designed to sync files (Apple likes to call it Documents) which is not a good fit for Snippets. I know there are some workarounds, but workaround is bad by definition.
If you still have any related question, you are welcome to ask them in comments.