Do you really need a high aperture wide angle lens?

Wide angle lenses are used. Period. One use is for "landscapes" but there are other uses where a large f/stop might beneficial (fashion, people, interior shots, etc.) or simply when for whatever reason one wants a "wide angle effect" at a large f/stop.

Personally, I'm less concerned about large apertures on my wide-angle lenses than I am on my telephoto lenses, simply because it's relatively difficult to achieve a shallow DOF on a wide angle lens (yes, it can be done, but the effect is seldom as dramatic as on a telephoto lens). The only time I might want a wide aperture is in situations of very low light. I primarily photograph landscapes, and I nearly always use a tripod.

Just to be clear: "high" isn't a particularly helpful word in this context. When referring to a lens, you might say that it is: "Fast" - meaning, it can be opened up to a wide enough aperture to let in a lot of light ... which allows you to use a faster shutter speed. This ability to shoot with a big aperture opening usually means more glass and thus bigger, heavier lenses that cost a lot more to make well.

The larger the opening, the lower the f-stop number. So, a lens that can only open up to f/2.8 is slower than a lens that can open up more, to f/1.4. An f/2.8 lens is slower than an f/1.4 lens.

You're not missing anything... for a dedicated landscape shooter, a set of high quality f/5.6 or f/4 primes would be wonderful. However, most of your dedicated landscape shooters are lugging around 4x5" cameras so Canon has to target its lenses at a more general audience.

So they could make them and (if priced attractively) sell some, but probably not enough to make them profitable, which is all that really matters to Canon.

As with the others, its a larger/faster aperture (low f-number) or a smaller/slower (high f-number)

For several years I used a Nikon 28/3.5 which I never liked. Eventually I bought a Nikon 28/2.8 and gave the clunker to my Dad. Loved that lens. Once day in a fit of madness I swapped it (and some $$) for the Nikon 28/2 thinking the extra stop would be a real boon (particularly since this was back when film was king as Tri-X at ISO 400 was my staple).

Hated that lens and in particular was taken aback by the weight difference. Eventually I was able to go back to a 28/2.8 and I've never regretted doing so. YMMV.

Henry Posner
B&H Photo-Video

This is exactly why a lot of people prefer the 17-40mm f/4L over the 16-35mm f/2.8L; the IQ is very close and the 2.8 is unnecessary for landscapes. Not to mention the 17-40mm is much cheaper and lighter. However, the 16-35mm f/2.8L is a must for others, such as wedding photogs for getting the bouquet toss, along with other low light, wide angle atmospheric shots.

Anything you're missing? Only that some people might like to use a wide angle lens for something other than landscapes, and sometimes that something might benefit from having a fast lens. But don't pay for a larger aperture than you are going to need. Fast is usually expensive.

Sometimes a lens needs to be fast for reasons other than shallow DoF. For instance, consider shooting stars in the night sky. This is often done with a wide angle lens having a larger aperture. The larger the lens (physically), the greater the light gathering capabilities, the greater the success. Also a faster lens means shorter exposure, which means lower noise and less required exposure stacking.

As others have pointed out, sometimes a wide lens should be fast for reasons of focusing in dim environments.

Having said this, I don't think a background blur is particularly good or useful unless it can be an appreciable blur. Otherwise it just looks like bad focus. So I suppose I fall in the camp of preferring smaller/lighter/cheaper/slower/sharper wide angle lenses.

Thanks a lot for all the responses. Well, I have an older Sigma 15-30 on APC-S sensor and really like the results from it at f/8 - f/11, mainly used for landscapes ... but have been seeing some excellent shots from Canon 16-35 f/2.8 II (better than the ones from my Sigma) and was wondering if it was really aperture or the lens quality itself ... can you guys recommend a great landscape lens that is sharp and does not necessarily break the bank ... I don't make money out of photography but am passionate about it ... budget is less than $1k. I may upgrade to a FF camera in near future so would like to keep that in mind when buying this lens.
Does a zoom really help in ultra wide range ... I would prefer a prime if it is cheaper than zoom (with same optical quality) and helps in reducing weight and is cheaper, but am open to a great zoom as well.