It wasn't settlement only, but Spaniards did settle there. However, the nature of these colonies tended towards pure resource extraction in the sugar and mineral regions -- creating stratified classes.
Portugal did much the same -- they did not have dedicated settler colonies either, instead sending out degredados to Africa. Where they differed was less due to their style and more due to the unique conditions of Brasil that allowed for bandeirantes and a sophisticated, very large sugar complex. To echo points above, they got a lot of settlers once Minas Gerais struck gold. Overall, Portugal sent out ridiculous amounts of people relative to its size, esp. expelled "marranos", but they didn't found settler colonies in the manner that we'd associate with the English. Even Nieuw Nederland had the patroons, and New France had the seigneurs -- showing that even in non-tropical climates, that feudal relationship could and would be replicated.
Furthermore, these colonies were largely in tropical climates. Whites would come and die faster than they could replace themselves overall, which, combined with social norms and large native populations, largely lent itself to the creation of mestizo peoples rather than the perpetuation of old Spaniards in a New World.
Finally, unlike pre-Union Portugal, Spain had a number of Euro-Mediterranean entanglements, from North Africa to Italy to the Netherlands. Royal attention and funds were drawn elsewhere constantly.