Canon hasn’t introduced a standard (excluding macro and DO) non-L prime since 1995. Their line of thinking is probably that most folks buying xxxD and xxD cameras want zooms, and most folks buying xD’s want L’s. One could also surmise that because it’s been in production for over 18 years, the ROI is pretty high on it too. Why replace a high margin product with one that would require R&D, factory retooling, defect management, and marketing- only to have folks complain about how expensive it is?
I'm an enthusiast who owns a 5Dmk2, and here's what I think:
I bought the Canon 35mm f/2, and am not too happy with it. The 35mm f/1.4 L is too expensive for me - I can't pay U.S.$1,000+ on *every* lens I buy. Reviews say the Samyang 35mm f/1.4 is great. It doesn't autofocus, but at that focal length, I can live with that. I plan on selling the 35mm f/2 and buying the Samyang.
Reviews say the 24mm f/2.8 has mediocre IQ, and it's only 1 stop faster than the 24-105mm f/4 which I usually carry anyway. The 24mm f/1.4 L mark II is too expensive for me. Samyang has announced a 24mm f/1.4 lens. If it's price & reviews are like the 35mm, then I might buy it as well.
A co worker is in a similar position. He has a 5D mark 2, he has a 70-200mm f/2.8 IS II USM, but with a family to feed, he can't cough up price of L primes. Actually, all his primes are by Sigma (an 85mm f/1.4, a macro, etc), and he is happy with both the price and the photos.