You are thinking "source code".
"Code" is another term for what you are referring to as "binary".
"Code" is another term for what you are referring to as "binary".
An example that comes to mind is a high speed image compression app for taking rapid sequences of photos. Apple bought the company or the rights so they could include it themselves.
Software is only easier to write than read if you have an idea what it's supposed to do. If you've ever googled "how do I do X?", then you likely have reverse engineered the answer you found to fit your particular use case.
In addition, and in some countries, you can't patent software (thankfully), and so innovation comes through reverse engineering naturally.