There are exceptions from this rule. But friom th 4 civs you listed I would only count Mayans as one of them.
3 civs have Gold Bonusses that are sufficient enough to justify double Gold:
Mayans, Malians and Portuguese…
Some civs have quite bad trash wars and want to end the game before:
Franks, Mayans, Aztecs, Cumans, Celts, Gurjaras, (Turks)…
Some civs have interesting alternatives that synergize well with a double gold comp play like
Franks, Gurjaras, Turks, Incas…
And then we have one civ that can go for double gold cause of one insane tech
Poles
And ofc we always have that clownery stuff going on in arena.
If you are interested, I made once a Thread about hypothetical Trash units that could be made to synergize well with the gold units in the game that currently don’t have a natural trash partner: