Why do companies ghost after interviews?

Recently started giving interviews and cleared a few rounds in a couple of companies. I never heard back from any of them even if I felt the interviews went well. Very frustrated because of this as I fail to understand how difficult is it to just reject or send a rejection email if they don't want to hire. I understand that companies have 100s of candidates in their pipeline but it's so frustrating to not even get any rejection mail and get stuck in a limbo.