Why? Inevitably, I changed positions / jobs / platforms, and all that effort was lost / inapplicable, and I had to relearn to use the stock settings anyway.
Now, I understand that some companies have different setups, but it might just make more sense to change the company's accounting procedures (if possible) to conform to most accounting software defaults, rather than invest heavily in modifying the setup, unless you're a huge conglomerate and can keep people on staff. Why? Because someone, somewhere will have to maintain those changes. Sure, you can then hire someone else to update those changes - but guess what? Most likely, unless they open-source their changes, no LLM will have seen those changes, and even if they are allowed to fine-tune on it, they'll have seen exactly ONE instance of these changes. Odds they'll get everything right, AND the person using the LLM will recognize when it doesn't go right? Oh right, they invested in hundreds of unit tests to ensure everything works as expected even with changes, and I'm the tooth fairy..
I don't actually think this is going to take the form of LLMs implementing custom patches to off-the-shelf software. I think instead it's going to look like LLMs writing code that uses APIs offered by off-the-shelf software to script specific workflows.