Hey, everyone gets a name, why not Null? Why should he be the only one referred to by his pseudonym?
Question basically was - why not give him a predetermined name - "John Doe" or something?
To me a customizable character helps me feel more ownership and relation to the main character. I tend to be more concerned about what happens to a MC I have personalized versus one that is premade and fixed in place.
Plus I'm a proponent of more choices in games. If you simply don't want to customize a name for a character or feel no need to the option is there for you to just use the default name and start the game. But for those that want to customize and have a bit more of a personal connection to the protagonist they are able to.
There is a lot of mediums without customizable characters - movies, books, comics. I can't say that characters depicted in them are less relatable by design. Isn't having all possible decision making in your hands as player not enough? And naming your personal instance of character "James" or "Peter" won't change the plot at all.
Choices are actually presenting interesting dilemma from perspective of design and writing. There is 2 approaches that can be applied player chooses something:
1. You have to take all possible outcomes of this choice into consideration. That means keeping number of possible options if not bare minimum than at least reasonably small. Additional option added to list - extra work at the spot and at 10 more spot down the line. More often this approach taken - more complex project becomes and overall workload increases. That is sensitive point even for large fancy AAAA-developers, for small team like Ron's - tenfold so.
2. You can make it purely cosmetical or ignore it altogether. You can name Null "Philippus Hohenheim", "Baron Samedi" or "George Washington" and not a single character will bat an eye after hearing that. This approach allows a lot of "customization" but at the price of significance of choice. Too much of this - and protagonist becomes some strange shoe-in figure in comparison to other character. Luckily, that's not our case. And won't be such a case, I hope.