"ALSA is an ugly carbuncle stuck on the side of the kernel source tree, and its configuration language is nearly incomprehensible -- and mostly undocumented"
IMO, PulseAudio would not have happened (the way it did) if ALSA had been properly documented, maintainable code, because the unfathomable, undocumented style of the ALSA project makes devs run as far away as possible from Linux audio subsystems.
Perhaps the developers didn't want anyone outside their team to understand the system. More charitably, perhaps they were so deeply immersed in the code that they didn't realize exactly how awful it is. I mean, it works great, but... when I wanted to port my windows audio drivers to linux, spent a few hours getting to know the ALSA code, and literally ran away screaming. Literally.
Beware the truly brilliant programmer, because they will write code that nobody else will be able to maintain.
Yes, something _like_ PulseAudio will always be necessary for "happy little user apps," but I believe the byzantine ALSA code has repulsed good developers away from the audio subsystem and left a developer vacuum the shape of PulseAudio. :(