Except for outlier cases, I've not seen the need for it, no matter the traffic of the site.
I've worked with sites that have done things like offload to Amazon S3, but my experience is a CDN effectively offloads from your server. They have a high enough image hit rates to cut down 90-95% of image fetches. It's more cost effective using a CDN like Bunny CDN or Cloudflare (which is often free).