It says it supports a gateway mode, but as a power user I want a bit more control than what I would expect a WAP to offer. I use an EdgeRouter-4 running whatever the latest official release is. Having separate boxes grants me freedom to do things like mess with Wi-Fi settings while my SO watches a show on Apple TV connected via Ethernet. It's the little things.
I often think of a pfSense build, but then I remember how happy I am with the performance and efficiency of a dedicated box.