Why? You can retry, but there is nothing wrong with increasingly waiting slightly longer if we fail many times.
Try asking Opus or Fable that question. It'll give you a good answer on why microservice architectures work the way they do in order to keep user-facing latency acceptable and minimize downtime. It's a complicated enough topic that I don't feel like explaining it for free to you in a HN comment.
"exponential" and "slightly longer" are very different backoff patterns.