I like to shoot city and landscapes. I saw that photographers often use tripod even during a day. Why would I need a tripod during a day, if I can get shutter speed like 1/125s even with low ISO? And I'm not going to need multiple shots (eg. for HDR or time-lapse)
There is a rule in photography: If you can use a tripod, do it.
OK, I just made it up but let me tell you why it is a good idea:
- Stability: No matter how fast your shutter-speed is going to be, a good tripod can do better. There is a rule-of-thumb that says you need a certain shutter-speed (1/focal-length) get a sharp enough image but it does not guarantee one.
- Creativity: A tripod lets you shoot at low shutter-speeds. Even though you could shoot faster, you may not want to. Maybe you want more depth-of-field or blurred motion.
- Precision: With a tripod you can set your camera position exactly and it stays there. Getting your camera level and keeping it level is much easier with a tripod. Plus, with the camera fixed there, you can take the time to check all your edges and composition without the view shifting as you do it.
- Repetition: You obviously know that HDR or time-lapse require repetition of precise framing but those aren't the only case where this can be useful. You may have taken the time to perfectly frame your shot only to suddenly have something unwanted move into the frame. With the camera firmly on the tripod, you can take the same exact shot after the unwanted element has been removed.
- Self-Inclusion: With a tripod you can put yourself in the frame. You can try camera tossing instead but you cannot control framing that way.
- Panoramas: Try rotating around the nodal-point without a tripod! It is much easier to get all the shots you need with a tripod and even easier with a specialized head with marked positions.
I do when shooting landscape/buildings for compositional reasons. I compose the shoot just the way I want it and then I wait for the light to be right. It might be a pattern of cloud, or the color of the sky, or the shadows falling around the building. I've been know to wait 45 minutes just sitting on the ground with my wired remote in my hand pressing the button when it looks good.
Other than allowing for longer exposure times, a tripod helps really a lot aligning the camera and composing city and landscapes scenes. Keep in mind that those subjects usually require more than one try at the same location, even if you are not planning something like a HDR or time-lapse.
With a tripod you can also use the camera timer (or a remote shutter) instead of manually pressing the shutter button, which minimises camera shake.
There is this article, about how to get photos maximally sharp. Rule 1 is to use a tripod at all times. So I guess main reason for most landscape photographers would be sharpness.