That's a bit unfair. :-) Hardly any bug trackers are intended for hosting diverse projects written in different languages, so hardly any bugtrackers let you search by programming language in the first place, so hardly anyone will have used such a feature yet. There may be reasons Launchpad shouldn't support this, but that people haven't been able to use it elsewhere isn't one of them.
The use case is, "I want to fix a bug, but I know only C# and Python".
That's a bit unfair. :-) Hardly any bug trackers are intended for hosting diverse projects written in different languages, so hardly any bugtrackers let you search by programming language in the first place, so hardly anyone will have used such a feature yet. There may be reasons Launchpad shouldn't support this, but that people haven't been able to use it elsewhere isn't one of them.
The use case is, "I want to fix a bug, but I know only C# and Python".