I was not satisfied with existing iOS Bitcoin apps, especially with BreadWallet (the one I mainly used) where development stalled and they could not even deliver such features as SegWit, RBF and custom fees (at the times where custom fees were especially needed).
So I knew I could create one to use myself and let others use it.
I had experience with awesome bitcoin-js lib (javascript), and since I dont own any Macs, don't plan to and not going to learn ObjC/Swift - ReactNative (where you also write in javascript) was an obvious choice.
Grab an issue from [the backlog](https://github.com/BlueWallet/BlueWallet/projects/1), try to start or submit a PR, any doubts we will try to guide you.