Double-glazing? It's very common here (the UK) - maybe you live somewhere hotter that doesn't need it.

It's called double pane. Two pieces of glass with air trapped in between. More expensive ones use argon or other noble gasses that transmit heat even slower. They're not common in older homes but most newer ones I've seen have them. The issue with upgrading is just the expense. You get used to your monthly utility bill but spending thousands on new windows that aren't "broken" can be difficult, even if they will pay off eventually.

There are also triple pane windows that are even more efficient but for the price difference they typically aren't worth it in most climates.

Insulated Glazing Units (IGU) are a thing where they make sense in terms of energy savings, and are often required by building code. They're less common in older buildings as we didn't used to be as energy conscious and their relative cost was higher.

Double pane windows are required most places nowadays. As to why they weren’t used more in the past, the folks that build homes want to make as much profit as possible in constructing and selling a home. They don’t have to pay the utility bills - that’s on the homeowner. Thus building a house with inexpensive, inefficient windows is better for the builder (or used to be) than more costly, efficient windows.

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