Apple Mail and IMAP – Removing local attachments only

I use an email provider that provides me with 30gb of space on their server.
Using IMAP, I send and retrieve emails on my laptop, iPhone and iPad using the default Apple Mail clients in each.

I do not understand why there's not an option in Apple's Mail client to remove email attachments without removing them from the server too. While I understand some benefits in having duplicates of your emails in every device and server that uses your email, its ability to choose whether attachments are also stored appears to be half-heartedly implemented:

• You can choose not to download attachments as new emails arrive
  locally
• You can choose to only retrieve the last 15 months of
  attachments, described as 'recent' in options
• You can permanently
  remove the attachments from all devices, including the server with a
  prominent 'remove attachments' option.

I don't understand the lack of an option to remove an attachment from an email (leaving it in the same state as it would have been had 'none' been selected as the option for attachment downloads in options) but retaining the attachment on the server for reference later, if needed.

I'm slow to move from Gmail for personal email for this reason. Using it avoids filling up my devices with space that I'm fine to leave on the server (and use only through my web browser). I'd rather use an email provider and client from a third-party that's not Google but I can't find a way to efficiently return all local emails to text-only after I'm finished with them without also removing the attachments from the server or having to use a cumbersome folder browsing method or third-party utility. Gmails primary advantage to me is not using space on any of my devices.

Do those who lament how quickly their phone's space fills up not also want this option when it's perfectly possible to implement? I'm fine with the reduced backup safety of only having the attachments in one location (the server).