If an individual modifies a piece of hardware the potential impact is limited to that one piece of hardware.
If an individual modifies a piece of software, that software can potentially proliferate over many pieces of hardware. It can be unloaded and replaced with the original manufacturer's software without leaving a fingerprint. It may not even be possible to distinguish the modified code from the original through the layman's interfaces.
I am a real, professional software engineer with thirty plus years of commercial experience and I don't like the idea of hacked code, i.e. that code differentiated from code which has been through a professional, controlled QA and release process. I certainly wouldn't like the idea of my own code being hacked by someone claiming to be a software engineer unless they have applied those same rigorous professional standards.
There is also the "look what clever thing I done, it was so easy, you must be dumb because you didn't do it yourself?" factor which is ignorant, disrespectful and patronising. There may be a whole bunch of commercial reasons why a commercial software product lacks features or is delayed in the release cycle, some of them nothing to do with functionality, market demand or technological capability.
I would also be concerned about IP issues. If I, as a hacker, change 99% of the code it still isn't my product because I didn't design the operating environment, the interfaces, persistent data storage schemas, documentation standards, back-out plan, upgrade paths and all those annoying things that concern a professional software engineer and which are conveniently ignored by the hacker.
So I guess my argument is there is more to code than the run-time program file. That file relies on a whole bunch of other people's effort and work product still being in place and working. And it may work today but not tomorrow after, for example, after a hardware change caused by a regulatory recall or other event within the responsibility of the manufacturer but outside the realm of the hacker.