Bihar is one of India's most underdeveloped states, with high levels of poverty, unemployment, and low social indicators. The state has been struggling with underdevelopment for decades, and several factors contribute to this situation. In this answer, we will look at some of the reasons why Bihar is still an underdeveloped state.

1. Historical factors: Bihar has been facing underdevelopment for a long time. The state was ruled by various dynasties and colonial powers for centuries, which resulted in the exploitation of the state's resources and people. The British colonial government, for example, treated Bihar as a resource-rich region and extracted its resources, leaving the state impoverished. The lack of investment in education and infrastructure during this time has also contributed to Bihar's underdevelopment.
2. Political instability: Bihar has a history of political instability, with frequent changes in government and coalition politics. This has resulted in a lack of continuity in development policies and programs, leading to a sluggish pace of development. Corruption and nepotism in the political system have also hindered the state's progress.
3. Poor infrastructure: Bihar's infrastructure is inadequate and outdated, which has led to a lack of connectivity and access to basic services. The state's road and rail networks are poorly maintained, making transportation difficult. Power supply is also unreliable, and many areas do not have access to clean water and sanitation facilities.
4. Low literacy and education levels: Bihar has one of the lowest literacy rates in India, with only around 63% of the population being literate. The state also has a low enrollment rate in primary and secondary schools. This has resulted in a lack of skilled manpower and low productivity levels.
5. High levels of poverty and unemployment: Bihar has high levels of poverty and unemployment, which has led to a lack of economic growth and development. The state's agricultural sector, which employs a significant proportion of the population, is characterized by low productivity and low wages. The lack of industrialization and job opportunities has resulted in a large number of people migrating to other states in search of employment.
6. Lack of investment: Bihar has not received adequate investment in infrastructure, education, and healthcare. This has resulted in a lack of private sector development and low levels of economic growth. The state's limited resources and poor governance have also hindered investment opportunities.

In conclusion, Bihar's underdevelopment is a complex issue that has historical, political, economic, and social dimensions. Addressing these challenges requires a long-term approach that focuses on improving governance, infrastructure, education, and healthcare, and creating job opportunities. The state and central government, civil society organizations, and the private sector need to work together to address these challenges and create a conducive environment for development.