laclongquan
Arcane
You gave the motive in your original post - if there's a risk that non-legitimate children inherit the powers then there's a reason not to make them. Especially given that magical contraception methods don't have any of the disadvantages condoms have.Mage nobles, simply speaking, has no motive at all about contraception.
There's also a very obvious motive for contraception for female mages.
But then again, I also don't agree with this:
Because you can just use magic to increase your quality of life indefinitely.you dont want to expand your noble class size too much to keep your quality of life high
No. Legitimacy only means something when it means something REAL. In a mage-noble society, to be a mage is legitimacy, not anything else.
In a non-mage noble society, legitimacy is just something you use to limit the inheritance to ONE inheritor, or a close select group. Said inheritance is lands, positions, wealth.
In a topdown mage noble society, what's real is magic skills, magic knowledge, everything that differ mage-nobles to nonmage-nobles. Most especially if magic is something in the blood (genetic). Which means you can not make mage-noble at your will. If you dont have your proper successor as mage-noble, all you accomplished will be nothing because your children will be a nonmage nobles, or a normal. With magic like that, to have a proper successor is EVERYTHING.
To keep it simple and Earth-like for you to understand. Let's take an example, say a society that is EXTREMELY revere quantum physic. You either have to understand quantum physic and be the top, or you be everything else. If your family dont have one understand it, yours is second class. If yours have one, that one generally is the leader in the family, or at least the one with right to command. If you are the leader of such a family, do you concentrate on making as many children as you can in order to have one that can understand QP? Or do you use contraception to make as few children as possible, and therefore risk you dont have even one child to understand QP? IN which case your next generation become second class. Rich be damned!
And if you dally with a servant girl in a bar downtown and she bring a child that's extremely possible that can understand QP... do you take that child as your own (and every trouble that come from it) or do you ignore that as unexisting?
In such society, the former option is obvious. And it's why they will not use contraceptive. Because Quantum Physic, man!