CCM singers do it all the time. They have the luxury of singing with a professional band during their singing lessons. Classical singers sometimes have to be contented to singing with no accompaniment at all during lessons, or having their singing teacher play with varying fluency and then finally and preferably with a professional skilled pianist, another artist. The latter is of course what we all want and love. Although, sometimes a beginning singer may feel intimidated by the professional musician, not knowing his/her music perfectly, perhaps missing entrances or making mistakes in counting the rhythm. How about having practiced with playback, learning how the accompaniment sounds even in the most difficult pieces that the singing teacher maybe even refuses to play? Here is one possibility that so far has eluded the typical classical singer.
Now there are resources available to all singers, with lieder or arias. You can sing with a conductor with the e-Vocal program available in the Internet. You can order your piano accompaniment for many songs from a website called Your Accompanist. You can even sing arias with a full symphony orchestra listening to special CDs that offer the repertoire for all voice types.
My opinion of using playback with classical singing is mainly positive although there are obvious reasons why it might not be applicable. It can be good for your initial rehearsing, before you meet your professional accompanist for the first time. You will be better prepared, but do not be surprised if the tempo is a surprise. You will perhaps get frustrated because your digital accompanist doesn´t know where you breathe but on the other hand, that can help you keep the tempo at all times. It is unflexible, maybe even unmusical, but what a relief when your in-person real pianist listens to you and lets you make nice tempo changes and rhythmic nuances. Then you really know to appreciate your partner!
So, very good for some rehearsal purposes. Definitely no good for the final artistic development. And absolutely forbidden in performance! This is just to say, don´t even think of saving the pianist´s fee if you asked to sing a classical song in public.