When using a URL to upload images, users get an error.
"This image cannot be used in Jeto due to your server settings. Please download it to your computer first, then upload in Jeto"
Images have to be on Public images server to be shared.
Marketo server is not allowing images to be loaded by 3rd party servers and as a result users are not using this feature.
This was pushed with the Dec'21 - Jan'22 release.
Please upvote this feature if it's important for you.