Zodiacs were only in the first two base game Sims packs as far as I am aware, getting into Late Night in Sims 3 later but maybe they might be included in Sims 4 so as to put Birthdays into the calendar to be remembered year by year if you have the Seasons pack.
You could include the Zodiac as a base game addition just to set the Sim's traits or attraction to other Sims in certain zodiac signs, not using the calendar feature if you haven't got Seasons though.
I don't see any objection to zodiac signs being added free but would object to a main element of Sims 4 Seasons pack being added to the base game.
