Purely so they can have a self-satisfied holier-than-thou smirk. There is absolutely no reason that the early admission program inherently creates barriers to disadvantaged. Rather, it was Harvard's greediness to increase its yield rates by taking loads of students early that creates the problem.
If they wanted, they could take fewer students early, and make sure that there were plenty of spaces left for students who might not want to apply early (or might not be aware or otherwise couldn't get in) and take them during the regular application process.
