Wikimdia mailing lists originally have the -l suffix as they were formally under wikimedia.org. Since the move to their own domain (lists.wikimedia.org), the use of -l in lists has been discouraged.
There have been talks and plans of standardizing lists however renaming them was always deemed too much work and not useful. Regardless, removing the suffix would unify all list names and be more logical.
Wikidata-l will be renamed in T99136 which will trial the process and see how easy this is in production and practice. If this is deemed practical, allocating times and days to work on a few lists at time over the next 2-4 months would finally resolve this task.