We are still human though, and sometimes it can get a little uncomfortable wearing robes, especially in the heat. We get sweaty, especially the left arm which is wrapped in the robes ‘sleeve’ and some people get heat rash. It is hard, sometimes, in a hot meditation hall, wearing robes in a formal way, because the can constrict the left shoulder and neck a little if you wear it too tightly, but you can loosen them without looking too sloppy. Certainly, in less formal contexts and in the privacy of our own huts we don’t need to wear the robes to meditate and can be more comfortable and cool.
We only have one set of robes, so we don’t have a winter or summer ensemble, but in winter we can wear layers underneath. Our set of robes also includes a double layered outer robe that can be worn individually, or wrapped together with our upper robe for 3 layers in total.
Robes are a very practical garment! They can be used as clothing, shawls, sheets, shade cloth and even tents. They last a long time (my current robes are almost 4 years old) and can be easily patched, as well as being relatively easy to wash and quick to dry. After they are worn out they can be recycled into curtains, patches for robes, rags or whatever. However, robes are a bit less practical when it comes to doing more physical things, especially one shouldered, there’s not much structural integrity there at all.
Another interesting point in regards to @Polarbear’s original post, is that the sekkhiya rules tell us to go well covered in inhabited areas and the commentary defines that as you noted above. Mostly this is interpreted as both shoulders being covered but some schools such as the Siam nikkaya of Sri Lanka do not follow this and wear only one shoulder covered in public. I think in Thailand some novices will wear only one shoulder covered in public. I wonder if that is to distinguish them (and their behaviour) from the bhikkhus. I also recall some controversy about the shoulder issue in Myanmar.
In Sri Lanka, monks and nuns simply drape the robe over the left shoulder, without the rolled sleeve of the other Asian traditions, which seems more comfortable and practical. Thus looks more like the images of the Buddha depicted in sculpture. The Burmese monks sometimes roll their robes in the most fascinating way, including creating what my friend called the “throat lock”, which is almost like a collar. I imagine that there would have been countless ways to wear robes in the past when robes were all the rage in the general population, and that’s why there are the style prohibitions noted above.
For a fascinating masterclass in robe tying styles, see this video by Sayadaw U Nandasiddhi, which has a breathtaking variety!
[In the following videos you might want to turn the volume off. ] This first one is the style of robes usually worn by monastics in the south East Asian tradition (and international forest tradition):
This is an example of city monk style, a more practical arms-free one shoulder, fastened by a belt:
This is the Burmese style:
Antique photos show that the way robes have been worn remain remarkably consistent in the modern period at least. This beautiful old photograph shows Thai tudong/carika monks with robes fastened by a belt and the sleeves rolled up for more freedom of movement
But this is the style people have recommend for me!