Because it's very simple. Canon and Nikon have an established reputation and lineup across a wide range of segments that most people trust and use. Because of that established public image and history, most people have lens or a history with the products that leads to them to continue using such product. Sony is simply not a household name for its photography equipment. Video equipment is a different story.
Sony doesn't really offer any compelling reason for the consumer/prosumer to switch their camera brand. Sony also simply doesn't offer the type of professional grade camera equipment that Nikon or Canon does. So their market penetration is going to be low because they are not the established leaders and they really don't provide anything that would significantly sway the opinion of the mass public to use their products.
Not to mention that Sony as a whole is downward trending on their image. Rootkits, C:13, Playstation Network down for several months and more. People don't want to buy products from a company they can't trust. Canon and Nikon on the other hand don't have these issues and people trust their cameras. So it's those several reasons that keep people buying Canon and Nikon.
LOL psn down for several months? Exaggerate much?
Rootkits are bad, very bad. Sony's music IP arm needed the pummeling it got. I can't believe i'm defending Sony, but in a company as big as Sony you have to be a fool to think that the right and left arms are coordinated. What the Playstation arm does most likely has ZERO connection to what its camera division is doing, and that isn't really connected to the division that makes TVs, music players, etc. etc.
All the haters are just haters living in a pipe dream if they think that Sony is an evil empire company purposely orchestrating everything. Its exactly like how Samsung can sue Apple and be the main supplier of chips - massive multinationals have divisions that operate like independent companies.
Canon/Nikon may not have the image because
they sell nothing beyond optical products .
Ideally, you'd recognize the difference between different divisions and base quality on the actual product, not your perception of the company as a whole.
This is a tech forum....not too much to ask for.
Of course i agree that to make someone switch, the value proposition of the switch needs to be MUCH MUCH higher than what you currently have. It isn't okay to meet or even barely exceed it, otherwise it isn't worth it. i have no idea how sony supports pros, but I'll assume they don't have the professional services that Canon or Nikon offers...but perhaps they are after a different market.
The NEX series is awesome and its clearly a consumer product for those who want P&S features with an APS sensor and other SLR characteristics (replaceable lenses)
Their more traditional SLRs are also aimed to consumers.
Even their ~2K USD SLRs are not clearly aimed to pros if the service packages are not offered. Its the same thing with Nikon/Canon....I see plenty of people with 5Ds and D700s that are not making a living off of cameras - expensive prices does not mean you are targeting the professional market. Of course, I rarely see anyone carrying anything higher that isn't making their living off of that. Different markets exist, and Sony may not be aiming for them with their products...
Anyways, in general, people have perceptions and can't break it. I haven't really analyzed a photo from Sony recently, but in the past they had NR issues. Not sure if its still a problem today. I'm also somewhat used to it - I've been hearing back to 2006 when I first got my Pentax SLR that Pentax is dead/dying. Nope, its 2012 and they are still around. Eventually people will grow old and senile, and the new generation won't listen or give a shit.