Hi Jonny. Yep...artistic reasons and probably other reasons we who aren't in the business can't imagine. It's not all about entertainment. It's also about big business, with unions, music publishers, lyricists, composers, artists who introduced the song, their managers and others all involved. In the case of older songs line the ones to be sung tonight, there may also be heirs to the songwriters/original owners involved.
Pickler's grandpa is going to be on the local news tonight, talking about her critics. Hmmm.