Tissue culture has many advantages. Some plants are carriers of virus or disease. Tissue culture is one way to rid a cultivar of the virus. Keep producing it and then testing for virus until clean.
Now I've done tissue culture with lilium, but the biggest advantage to tissue culture, in my opinion, is embryo rescue. Lilium seed does not have a protective coating, so you can remove the embryo that's visible and place in a test tube with a grow medium. The purpose is to create crosses with plants that aren't known to be fertile, but once in a while might still make a viable seed.
Doing tissue culture is also prone to contamination, so nothing is guaranteed with it, at least at home anyways versus in an actual lab.
