Maybe not a default because not everyone wants that. It is on the enhancement request list for consideration.
I agree that not everyone would want it and that it would need to be an option if it were supported.
I think the bigger issue is that the Add Person screen doesn't work very well. I'm not sure how I would suggest that it be improved. I would simply note that I tend to put the bare minimum of information into the Add Person screen to get the person into the system, and then I quickly switch to the Edit Person screen so I can do my actual data entry with all the necessary tools at my disposal.
Perhaps the Add Person screen could be made to look more or less like the Edit Person screen so you could add sources and media and everything else you need to add. And perhaps this "Add Person screen that looks more or less like the Edit Person screen" could include skeleton birth, death, and burial facts that wouldn't really be included at save time unless some data were entered into them. I don't really know what is best. If adding people worked the way I'm describing, I might actually hate it. It's a hard problem.
I think I remember Bruce saying that he had tried a lot of different variations on the way the Add Person and Edit Person screen work to try to make them better, but that none of the things he tried actually worked out very well. As I already said, it's a hard problem.