Historically there might be usage of hardcoded references in Salesforce Org and there are different reasons it impacts the org in different ways. If you would like to update here is what explained how it can be done.
- Go to Developer Console -> Edit -> Search all files and use specific string for search Or Use short cut Control + Shift + H to search all files.
- You can search the entire list and then select them to update.
- List of all the email templates and categorize them by Standard non code templates and Code(HTML, VF) templates
- For the standard templates replace the link with Detail Link merge field.
- For any code used one see if you can use the Detail Link merge field if not create a custom Label and use it in the template as {!$Label.LabelName}
