Depends on people, but for most it's mainly because Stallman says so. You still have ethics ground if you think it the same way as repairability, actively bloc

Depends on people, but for most it's mainly because Stallman says so. You still have ethics ground if you think it the same way as repairability, actively blocking ways to repairs things you bought yourself is questionable, and keeping things closed source can be seen as a way to artificially prolonge a strict dependance on your vendor by impairing your ability to resolve issues by yourself.