PC Street Fighter IV was a strong seller globally but it was also "number one in piracy." Ono-san appreciated the love for the series but hard sales matter.
This means that Super Street Fighter IV is only playable in the arcade and on the Xbox 360 and PS3 consoles. While piracy did help spread the Street Fighter name around more Capcom can't accept the IP would simply be "free" in certain areas.
Unless some form of powerful copy protection was found, Ono-san says they'll continue to give PC a miss for the series. SSFIV already runs on Taito's DirectX-based Type X2 arcade board so a PC version wouldn't be much of a stretch as it's practically ready.
He also ruled out a digital-only release because not everyone has access to online distribution platforms. Super Street Fighter IV releases on Xbox 360 and PS3 April 2011.