Why did Colonial Spaniards mate and had kids with the natives in Americas while the French and British were more "race-pure"?

To my knowledge, there were several factors at work.

Now first let me reframe the question to "Did Colonial Spaniards mate and had kids with the natives in Americas while the French and British were more "race-pure"? in order to avoid a deterministic, suggestive or even manipulative approach on the question.

In the areas, the Spanish entered first, there were these two indigene empires, the Aztec and the Inca empire. There the population was 10 or 20 times higher, than in north America.

The conquerors were mainly men and in the need of mating. Also belonging by the successful conquest to the ruling party, their social position was higher, compared to the Spanish homeland. And many conquistadors stayed where they were, building family, estates and property. Then Spain was a aristocratic country and the indigenous empires were been accepted on the same level too. So top level conquistadors, being in the homeland lowly aristocrats were marrying into the high nobility, lifting their social status up at some scale. So these three factors were, for the Spanish invaders and their foreign mercenaries too, quite an attractive lifting up possibility of their social status, in order to settle in the colonies and marry to the indigenous population.

Together with the attraction of becoming a noble, the catholic faith had an earnest interest, to win souls on an equally entitled level. So the locals were been courtshiped and in case of changing faith and converting towards Christianity full-heartedly embraced. That included open access to climbing up the cleric hierarchy.

Then the first allies with the Spanish conquistadors, were in the proceeding conquest strongly preferred and promoted in taking over subaltern positions. But once taken over these positions, they were kept and handed over among themselves. This entitlement was inherited, not taken away later from the Spanish again.

These aristocratic, cleric and political positions have been manifested till today.

So while there is still plenty of discrimination in many parts of south America, it still much less depends, to which “race” you belong, then to which historically grown social class you belong.

And as I was describing the development of the privileged elite, that was the exemplary role model for the low ranking ordinary folks. Mixing was so much more likely.

That explains, that and why the colonial Spaniards mate and had kids with the natives in Americas while the French and British were more "race-pure".