(I'm sure many of you have read all this before, but being fresh to the hobby I had to get it off my chest.)

So I've been looking for a fast prime lens for my T3 for a while, I could just buy one of the many great prime full frame lenses out there, but I couldn't shake the feeling that I'm not getting the most out of the lens if you go that route.

My understanding is that f-stop numbers on any lens give the same exposure (the amount of light per square area directed to the sensor) regardless of sensor format. The "aperture" or size of the opening in the front of the lens, is directly related to focal length in order to keep the amount of light collected the same across all lenses at the same f-number. There seems to be a huge oversight though.
There are no APS-C lenses that give the same field of view as a full frame lens at the same focal length.

Currently, all APS-C lenses act just like a full frame lens, giving a tighter field of view at the same focal length. To make a 30mm "equivalent" for APS-C bodies, camera companies just make a small 18mm lens and call it a day.
What would happen if you made a 30mm lens that produced the same field of view on APS-C as a full frame lens on a full frame body? Your image would be one stop brighter! Sounds like a win-win situation to me! If you're specifically going after a fast wide lens APS-C can get you an extra stop of light for free. With wide angle lenses generally being sort of slow, but useful indoors, you would think that someone would have made a big deal about that extra stop of light by now. If you're after telephoto, an APS-C equivalent to a FF 400mm lens would either weigh and (theoretically) cost half as much, or give the brighter image at the same size/cost.
Which means that if you went out and bought a 400mm f5.6 to use with an APS-C body because it's the only reasonably priced way to get quality telephoto, you can rest assured that half the value of your lens is utterly wasted on that APS-C body.
If you would rather put money into glass than bodies (considering that APS-C sensors are an order of magnitude cheaper to make), it boggles the mind that Canon (or anyone for that matter) wouldn't be jumping all over the idea of high end APS-C native lenses. They could make them just as expensive, just APS-C would have some advantages, whereas right now it has no advantages.

We're also missing a very valuable tool to gain performance that would otherwise not be possible.
The equivalent of an f1 lens on digital cameras may only be possible with smaller sensors. Take a normal f1.4 lens, adjust it for a smaller sensor and BAM! You have an image brighter than can possibly be achieved on Full Frame.
What really perplexes me is that the sickness (trend) seems to be propagated across the entire industry. The Metabones Speed Booster seems to be the first product ever to acknowledge that getting a brighter image off the same size of lens by using a smaller sensor is even a possibility. Note how the f1 equivalent with that tool does not give more light? I'm assuming that's because the speed booster puts the final element in the lens much closer to the sensor rather than keeping it the same distance as on a full frame mount, so light hits the sensor at more extreme angles. Thus aggravating pixel vignetting.
Done correctly, just imagine what could be achieved with something like the Nikon 1 series, you could get almost three extra stops of light.
Unfortunately, everyone has their reputation to keep. We can't have people walking around with $300 cameras that work better than $3,000 cameras, that just wouldn't do.

Yes, there will be some sacrifice in IQ vs. Full Frame, a sensor with greater surface area will almost always get better IQ (just remember that has little to do with pixel size until you're diffraction limited). As far as the consumer is concerned though, we've had cameras that are "good enough" for just about anything for years now, and given that low light is such a common issue you would think that brighter lenses for crop sensor cameras would be strewn all over the place by now.

"Deep breath"

I'm done now.