Graphics cards are not coming out any faster than they have been for the past 20-30 years....
Hmm, not from what I have found. Just in the last 6 years there has been roughly 85 Radeon cards that have been out. The 6 years before that, there was 65. Well that's just from what I can see.
As well, you take a look at the technologies involved. Each card introduces better performance, and each 'set' of card series introduces something new. Even if you take a look at the consoles, Ps3 and the new Ps4, it's a huge leap in graphics alone.
So when i say "Take a look at the rate of which video cards are coming out! (Here's just an example) They are always pushing technology." it's exactly that. The economy (demand) for more powerful (yet efficent) computer components is driving the innovative industry.
"need more power scotty!"