Why are the public sector and private sectors “imperfect institutions”?

Please provide the best answer for the statement.

The private or market sector of the economy does not always allocate resources perfectly because of market failures or information problems. As discussed in this chapter, the public sector can be quite inefficient in performing its functions, because of voting problems, special-interest effects, rent-seeking, limited and bundled choices, bureaucracy, and political corruption, each of which contributes to government failure. Thus both the private and public sectors have their limitations or flaws from an efficiency perspective, and thus are imperfect institutions in efficiently allocating resources and providing goods and services.