Indeed, this is a common workaround when your editor has no proper syntax highlighting. Still, in today's world nobody would write in that style in other programming languages.
You see the same issue with other relicts, for example, Pascal back in the 90s. Old text books wrote Pascal in uppercase style:
PROGRAM HelloWorld(output);
BEGIN
...
END.
But in reality, everybody using e.g. the Turbo Pascal IDE wrote lowercase instead, because it easier to type and because of proper syntax highlighting:
program HelloWorld(output);
begin
...
end.
Maybe this is not so much about the maturity of the developers (as I assumed in the previous comment), but about the maturity of the tooling.
There's also a good argument for not relying on "proper" syntax highlighting which is not always available -- especially not for such a divergent language family as SQL.
Every RDBMS has its own set of keywords and reserved words, so it's pretty much impossible to maintain a "proper" syntax highlighting mode.
You see the same issue with other relicts, for example, Pascal back in the 90s. Old text books wrote Pascal in uppercase style:
But in reality, everybody using e.g. the Turbo Pascal IDE wrote lowercase instead, because it easier to type and because of proper syntax highlighting: Maybe this is not so much about the maturity of the developers (as I assumed in the previous comment), but about the maturity of the tooling.