They help you get attention for your newest publication early on. They build excitement for the book as others read it and publish their reviews on it. Now I want to read it for sure as others have said it is great. The more people are talking about your book, the better.
Keep in mind that ARCs are pre-proofread books. They are fully edited and formatted, but the final polish has not been done. On the cover and as a watermark, note that it is an ARC. Let reviewers know that. They should not be reviewing any proofreading issues in their final published review.
Have them available in digital and print format. Not everyone takes digital and some don’t even like print versions.