Because the entire camera is currently 3.5 years old.
Tell me what other electronic device you would buy "new" today that was released 3.5 years ago?
This gets into the split between consumer markets and professional or industrial markets.
For instance, I used to work for a company that made a type of game system. Our customers generally had a 3 year software upgrade cycle, and maybe a 5-8 year hardware upgrade. In general we produced new hardware models every 2-3 years but kept producing ones for much longer because customers wanted them.
Though if you want to talk consumer equipment, look at video game consoles. The Wii and PS3 are 6 years old, you can still buy them. The XBox360 is 7 years old, you can still buy them. The PS2 is 12 years old and you can buy them new.
Computers tend to be a bad example because the whole supply chain moves, it becomes more expensive to produce older models then newer ones, so there is no economic benefit to continuing to manufacturer something using older parts, which is why you tend to see these incremental 'oh, that chip is now more expensive, well, swap it out for the newer one and that is our release this year' ones.
You tend to get this 3 year cycle time when you are dealing with either supply chain issues, or consumer upgrade fashions. Once you get away form those two areas you start to see things that stay in manufacturing a lot longer because industrial and professional work tends to be much more stable... not to mention more grounded in 'does this spec meet need X?' as opposed to 'oh boy, more Y!', thus buyers are less willing to pay for upgrades that do not actually benefit them in some 'demonstrable to accounting' way.