So in a case like email it's a local shim to sendgrid. What this essentially means is you have one service that's storing your API key and gatekeeping access to sending email rather than all of them doing it independently.

In the DNS case is basically DNS over HTTP which might not be useful to you since you can implement it but to someone who doesn't coslde it's useful.

Image service is storage and serving on top of micro which arguably yea you can do elsewhere and the wrapper to imagemagick you can do yourself but we've found there's a ton of people who just don't want to reimplement this logic.