What are the disadvantages of dialects?

The most important thing is communication. In fact, this phenomenon is common not only at home but also abroad. For example, there are many common phrases in standard British English that can't be communicated with Americans, even in Britain. But I personally think that although it is important to promote Putonghua, it does not mean that dialects will be ignored or even excluded. After all, dialects represent local culture and local characteristics. It is the dialect that adds a lot of charm to our life. For example, the cross talk between Hou and Ma, isn't it? In fact, sometimes people can learn Mandarin more effectively only if they really know their dialects.