Because Intel sucks and hasn't made a new chip in 5 years. RIP Gordon Moore.
It's not that they suck... they have great designs and ideas, but they have ZERO pressure to invest tremendous resources into developing a radically new chip design, because the competition is not there.
For the markets Intel has dominated, they just don't have competition. In the server industry, they do have competition in certain specific markets, or have been completely run out of other market segments.
In their current dominant spaces, all they are focusing on these days is incremental performance gains while striving to bring great power efficiency. Which is nice to have that, and hopefully their understanding of power efficiency means that, in time, once they are challenged, they can bring about a brand new chip design that is still quite efficient.
I very much hope AMD's Zen chips bring them back into actual competition for the performance crown. Intel only makes radical moves where they seriously rethink their designs when AMD makes a better chip.
Once they do that, then they have a few generations of large performance increases as they improve upon the new design. But now, we're at a point where they are really just increasing efficiency, and adding more capabilities or enhancing various bus speeds and bandwidth. Which alone can make it worth it.
I'm debating if I want to do a new build with Skylake or the chip after that. I'd like to have the improvements that platform brings to the table, but certainly it wouldn't be for a major gain in CPU performance, not for my uses.
But if you are a gamer, it is nice to upgrade from the Sandy Bridge platform, because that means moving from PCIe 2.0 to 3.0, and with current GPUs and games, it can make a difference. It's finally getting to the point that that is becoming an issue on PCIe 2.0 boards. Of course, that's only when the resolution is pushed and/or it is a multi-GPU setup.
I've been on my i7 2600K since it was relatively new (after the SATA issue was resolved).
But I have upgraded once on the GPU front (from 560 Ti in SLI to 290X in CF), added RAM (from 8GB to 16GB), and upgraded to a larger SSD to hold all my games.
The leap Intel made from Pentium 4 (oh what junk) was an interesting evolution, taking a more efficient and shrunken Pentium 3 design, enhanced a little bit, and released that for laptops. Pentium M was a major advance. They made a few iterations, improving upon the Pentium 3 essentially, scrapping the entire Pentium 4 design library, and then the Core was born, and then the Core2Duo took the world by storm. That lasted for awhile, but then they continued to run with that design as a base, and brought out first of the new Core series with the i7-XXX series. That brought a pretty big gain in performance. And then Sandy Bridge came out... and they wiped the floor, destroying the 3-digit chips. And they were cheap in comparison, more efficient, etc.
No chip has brought such an evolution in performance since Sandy Bridge.
And I guess I'm kind of hoping such a leap happens sometime soon, and I think a lot of people are sort of holding off until the next Sandy Bridge.
I just hope Zen isn't a let down.