Though there is evidence of a small number of true arches built in antiquity before Roman times, most acheologists back then considered the concept of the arch - illogical.
Not only that, these naysayers made archilogical digs at anyone who claimed they'd uncovered one.
Lintelectuals throughout that long dark archless period of history just kept telling the masons to keep repeating the same old design in more fanciful variations on the stone post-and-beam theme.
Broch Dun Dornaigil 2000 BCE
Lion Gate of Mycenae 1425 – 1190 BCE
The Treasury of Atreus - Mycenae -13th century BC
I druid on photoshop.
Here is what Stonehenge could have looked like if they had just done a lintel bit more architectural thinking back then.