Comment by CamouflagedKiwi

Because you know that the current one works. If you have a bank running on COBOL (or whatever), you've had that for 30+ years now, so while it might have bugs, you know what they are. You don't know what the LLM output is. Hence back to my original point: writing the code is not the hard bit. Making yourself (and your CEO etc) comfortable to put that into production is one of the hard bits.