Look for the other reasons behind this. In reality, seeing noticeable progress when learning a musical instrument or training the voice usually involves an investment of 30 minutes of lesson time along with just 30 - 60 minutes of practice over the course of an entire week.
If the issue is less "I'm too busy" and more of “I don’t really like it that much,” consider investigating a bit more. Has the student given the lesson experience sufficient time to really determine how much they like it? Have they they developed strategies for managing the sometimes overwhelming feeling of a new activity? Are they accomplishing enough "quick wins" to feel a sense of satisfaction? Often, these are easy fixes that require only a slight readjustment of expectations.