One may surmise that it doesn't suit her to provide never ending interviews.
1) It gives trump less ammo at the debate
2) Endless interviews have hurt trump. The black Jounalist, The NY economic club, that's why his numbers are dwindling, the Democrats are using the "let him speak" strategy, so therefore why should Harris do interviews pre-debate, she's riding a wave without them?
3) If your argument is she owes you, then let's make trump actually answer a question instead of the non answer word salad he gives us