Personally I think it should always be up to the author to dictate and decide how things are in their own stories. I trust that they have a reason for their choices and how they present their characters, world and overall theme. I find that trying to cater to what everyone wants often results in a mess and the quality suffers.
Yes, a lot of authors of interactive fiction have jumped on the bandwagon of allowing the player to choose all of the RO's genders and some people like having that freedom, but then you are denying your characters having in-depth backgrounds. How can a character that is supposed to be a closeted gay man explain his suffering if we tell him he isn't allowed to be a man? When will we hear the joyous story of a NB person realising that neither gender fits their identity and so they have cast off such labels and find themselves freer for it? In this authors case, maybe they aren't comfortable writing a NB person; perhaps they lack the experience to do so in a confident manner. They are least gave the player that option for their own roleplay. It's pretty similar for a characters race, they are things that shape and make them the character they are. Having too many characters could dilute the experience and/or put too much pressure on the author.
And then there is the problem of having one RO of every gender (or lack-there-of) and every race - it leads to far too many characters - the player will likely never remember all of them anyway - and the quality of all of their personal plots will suffer again. There was a time when authors were allowed their creative freedom and instead of being told what they "should" do with their own art, were advised by a small select few on how they could possibly improve upon it.
But all of this is just my own personal opinion (and everyone is entitled to an opinion) and ramblings, of course. Non of it is meant to offend anyone, merely offer an alternative perspective to consider.