The other factor has been the abundance of fuel. Ireland's various medieval overlords could never exercise the tight control over forest land that landowners did in more populous, less wild areas, like England and mainland Europe. This meant that Irish people had less trouble getting their hands on firewood. Where there was no wood, there was almost always heather, and usually turf too. As a result, anyone with a hearthstone could bake at home whenever they wanted to, rather than needing to use a communal bake-oven to conserve fuel.
These two factors encouraged the Irish householder of the past two centuries to bypass yeast for everyday baking. The primary leavening agent became what's now known here as bread soda -- just plain bicarbonate of soda, to US and North American users. Hence the name soda bread. But for a long time, most bread in Ireland was soda bread: "bakery bread" was only available in big cities. Soda bread was made either in a pot or casserole over the fire, or else baked on a bakestone, an iron plate usually rested directly in/on the embers. From these two methods are descended the two main kinds of soda bread eaten in Ireland, both north and south, to the present day.
The cake style of soda bread can of course be eaten hot. But it's more usual to let the loaf cool down before eating it (it's a little easier to handle then). It's also a lot easier to slice, and that's the way it's normally seen in supermarkets and convenience stores country-wide, in both brown and white versions.
One important note: in the US and North America generally, there's a tendency to think of soda bread as something with fruit in it. This is not the case in Ireland. While people have for many years sometimes added fruit to the basic dough as a treat or for a change of pace, this is not usually referred to as soda bread, but as tea bread, fruit soda, tea cake, and by many other names. We have recipes for these below as well. But everyday soda bread in Ireland does not contain fruit.
1 teaspoon sugar (optional: you can absolutely omit this if you prefer sugar free soda bread)
1 teaspoon salt
1 teaspoon bicarbonate of soda (+ 1/2 ts if you are using "sweet"/plain milk)
8-10 fluid ounces buttermilk, sour/soured milk, or plain ("sweet") milk, to mix
Let the bread alone, and don't peek at it! It should bake for 45 minutes at 400-450° F. (One of our Irish neighbors suggests you give it the first 10 minutes at 450°, then decrease to 400°. Also, if you have a fan oven, use temperatures 10° lower or so, as fan ovens have a tendency to run hot.) At the end of 45 minutes, pick up the loaf and tap the bottom. A hollow-ish sound means it's done. For a very crunchy crust, put on a rack to cool. For a softer crust, as above, wrap the cake in a clean dishcloth as soon as it comes out of the oven.