Is not as widespread as you think, you are hyper focusing on the ones you do see while out in public because it disgust you. A crow of 100 people and only the interracial couple will stand out to you because you dont like it. Point is its not as common as you think, races mostly mingle with their own races.
HOWEVER, this does not mean its not on the rise because 50 years ago it was rare but now is way more common not to mention acceptable. It also depends on where you live, if you are in new york or california there will be a higher number of interracial couples just because the place is majority liberal. How many of you have been in a shitty highschool where races date eachother? Me too.
I would also like to add that while a white woman may eventually settle down with a white man and have kids with him, this does not mean that they are not going to have skeletons in their closet. Many white girls may have dated or fucked other races but in the end go back to whites because they are past their whore experimentation phase.