Headstones have for hundreds of years been a way to honor our ancestors. They come in different shapes and forms, depending on where and when. In Valdres and Gudbrandsdalen, we have found wooden headstones. They were, according to Lokalhistoriskwiki.no, most common in the 1700s and 1800s.
You will find painted wooden headstones too, but the ones we have seen at Lomen Stavkyrkje, Vestre Slidre, and Sødorp kapell, Vinstra have been carved. The headstones found at Sødorp kapell is from right after 1900, and the ones from Lomen stavkyrkje are from the same period. So, these are dated much later than the article on Lokalhistoriskwiki.no claimed.
We would guess that carving the name on a wooden plate will first of all be cheaper than a headstone made of stone. Second, it would also be easier, since most people would be able to make them yourself. You only needed a piece of wood and a tool for carving the name and dates into the headstone. And by adding a “roof” to the headstone, rain and snow will not as easily destroy the headstone itself.