None, there is literally zero incentive to do so. All you will get is people complaining on your issue tracker, PR comments, etc. It’s better to write your own software and never release it to the external world.
Do you use any free software though? Ever file a bug yourself? I'm trying to see where you're coming from, but it's a bit difficult.
I have contributed a long time ago, before Github and recently. My point is that the incentive structure doesn’t align with the amount of effort that’s required.
You’re better off building something somebody needs and selling it. No reason to open source it, because the incentives are actually disincentives.
Believe it or not, but that type of community management is enjoyable for some and is incentivized to convey real benefits in both the social and financial sense. Also, even if you don't open source things you will still get users begging you for free handouts and unrealistic features. It's part of the business.