Classical songs are interesting. And they really sounds better if they are performed well and create a great impression to you. How would you like a classical song to be rendered... by chorale singing or solo?
I can still remember the disappointment years ago when I was feeling low and went out and bought a recording of Schubert songs. All of the piano parts had been arranged for orchestra.
Of course they should be performed well and create a great impression, but the composers knew what they were doing. Mahler wrote lots of songs with orchestral accompaniment. Doing them with piano loses something. Most composers wrote only songs with piano. Orchestrating them gains nothing.
There's always some kind of emotional content to a great classical song. The singer should convey that--even to audience members who don't know the language.