Does anybody know why the word always is written with one L, although it is formed by putting together two words, all and ways?
Middle English use of the word “all” and “al” were both recognized. 14th century constructions likely appeared as both “allways” and “always”.
In general, the codification of something like this often comes down to a single text that chose one construction. It is possible that something like the King James Bible or a particular author chose one spelling which was later emulated and eventually taken as the rule.