Why do enterprises keep two accounts? What are the advantages and disadvantages? Thank you for your guidance!

Originally, formal enterprises did not have the problem of two accounts at all. However, some enterprises have off-balance-sheet income, so they must have off-balance-sheet expenditure, so they need to set up another off-balance-sheet account. The establishment of two accounts is far from pros and cons, and the enterprise will not suffer, because the off-balance-sheet income of the enterprise circumvents the national tax (the off-balance-sheet income is definitely greater than the off-balance-sheet expenditure, so the enterprise will not lose money).