I would venture to guess that 95% or more are using the third party external (and some internal PCI card) sound card interface solution because it works, because it is convenient, and because the inputs and outputs available are easier to access, and it gives us a seamless recording experience.
BOLD: that would be my recommendation to eventually invest in.
Although I've mixed in the box for years I still have a mixer (3 year Behringer Xenyx 1622FX) which is actually just a glorified patch bay.
OP...glad you got things figured with your on-board sound choice.
Carry on....