I know that Canon has many great prime lenses, but all of them are EF lenses. The EF lenses, for full frame, are big, heavy and expensive, and of course unnecessary for crop sensor DSLRs.
Nikon, for example, offers 35mm f1.8 prime for crop sensor; the lens has USM, FTM (full time manual) and great build quality. Comparing to $1400 Canon's 35mm f1.4 EF prime, it has everything, but carries only one third of the weight, one third of the size and did I mention one eighth of the price tag too.
So I don't understand why Canon has nothing to offer for crop sensors, after all I imagine more than nine of ten Canon DSLRs out there are crop sensors.

There is one EF-S prime, the 60mm f2.8 macro. But I think Canon is just taking their time to see what the EF-S users are really looking for - and for Canon where is the most bang for Canon R&D buck. Right now the priority for that market seems to be mid-range zooms, which is what most people are probably asking for. Outside of that, EF lenses are compatible, so they can be good alternatives until something else is introduced.

But traditionally, Canon only releases a few lenses at a time. And many of the EF primes have been around a long, long time. My guess is if we do see more Canon EF-S primes, We will see something in the range of the 35, 50 & 85mm first, then the others focal lengths, might follow.

I do understand what you mean about the weight. The EF-S zooms I own are just about right on an EF-S body. When I stick a 16-35 or 24-70 on an EF-S body it's not pleasantly ergonomic. I had a photography assignment which lasted 7 days straight, on your feet shooting 4 hours a day, at the end of that week, I had all kinds of joint pains in my right arm in the wrists, elbow & shoulder, all because I was using Canon L zooms on EF-S bodies. In fact if I know that I don't need the color rendition of the L zooms I will always reach for the 17-55mm or put on a couple of EF primes, just because it's better balanced and lighter to shoot with.

In addition to Michael's excellent summation above, just thought I'd
point out that Sigma offers a full line of affordable crop-sensor primes
with Canon mounts. So there is that alternative.

Thanks guys. True, there are 3rd party options, but all of them somehow adopt the Nikon conventions even though they are made for Canon--- I mean the focus ring is reversed from Canon. Its frustrating to use on videos as manual focus is used all the time. Somehow it makes you feel you always have to get a Canon for the real solution.

Forgive my ignorance but I have a 28mm f1.8 and 50mm f1.4 that are both Canon and perfect price and weight. I know these are not ef-s lenses. Since there is no ill-effect to using these on a cropped sensor camera, why would Canon double their efforts? A little math gives you the true focal length.
That said, the thing I would like to see a full manual lens but I'm not holding my breath there as most consumers want the electronic assistance. And us video guys don't make up that much of their market.