With ASIO on Windows, all the user need do is install the driver and then select the ASIO device in their application. On Linux, if something is wrong with your ALSA config, you need to break out the text editor and become an expert in ALSA architecture and configuration. I've seen enough lost souls in this situation asking questions on mailing lists that I am convinced it is a major problem.
As someone interested in deploying an end-user application to Linux, the fact that there is no plug-and-play "it just works" solution[2] for low-latency audio is a big problem.
[1] More specifically: resolving misconfiguration.
[2] By this I mean a solution that works by design, not by luck.
