A very well question asked indeed. There are many relevant responses to this question. However, my fair idea is the fact that traditional medicine was created along the generations as we humans descended upon each other and discovered the planet earth. Traditional medicine was (assuming) created from the most basic of tools and resources and they have less proficiency compared to the medicines of today.
There have been numerous medicinal advances up till now and curing an illness in most cases, has been easier than ever before. The disadvantage of traditional medicine is that it lacks the proficiency and efficiency in curing compared to the treatments available today.
Nevertheless, this not always the case. If it wasn't for the creation of traditional medicines, we would not have discovered the technology available to us today.