My reasons for absolutely requiring open source wherever possible:

• your code does what you say it does
• you have nothing to hide (like backdoors)
• the author doesn’t rug-pull us and start charging for the technology suddenly
• any technology I use can be modified to meet my requirements as they arise
• I decide when a product is obsolete
• I decide how a piece of software is provisioned, launched, updated, phased out, the lifecycle and feature set of the software should be able to be CONTROLLED BY ME
• I can fork the technology to give more back to the community by improving it.
• it could easily be a fed honeypot
• it could be malware
• I prefer to contribute to furthering the capabilities and toolchest of humanity in order to liberate other humans from tyranny.
• I prefer not to support (and am honestly suspicious of) other software engineers that don’t want to further the aforementioned capabilities and toolchest of humanity in order to liberate other humans from tyranny.
• Closing the code off is morally wrong and speaks to the ulterior motives of the author.
• obfuscation (which I view as security-by-obscurity) is a sign of a weak codebase and a compromised project lead in my opinion.
• closed source software is a non-starter in matters of privacy