1) Competitive prices
2) If you want some type of audio component, they usually make it, and it'* compatible with everything else they make. My big example is MiniDisc (which I am running right now), changers, and the such.
3) They've got a huge R&D budget for new products
4) Asthetics are usually pretty sweet, and everything matches (how bout those pentagonals!)
5) Bias...my father has preferred Sony since the 70'*.
6) They're not going out of business anytime soon, so you know they'll be there if you need support.
Hmm, what else?
'95 SSEi, few electronic mods (and a stupid coupler)
HU (Sony MDX-CA680, European Ver; Sony 4x3-ways; 91, 93dB)
Yup, that'* ISU