Why Is It Difficult to Perfectly Eliminate Basis Risk?
It is difficult to perfectly eliminate basis risk because the spot price and the futures price are influenced by different, non-identical factors that are constantly changing. These factors include: unforeseen supply/demand shocks, non-uniform information flow, the cost of carry being non-constant, and the reference rate not perfectly matching the hedger's specific spot price.
The correlation is never perfectly 1.0 over time.
Glossar
Basis Risk
Exposure ⎊ The core of basis risk within cryptocurrency derivatives, particularly options, stems from the imperfect correlation between the price movements of the underlying asset and its derivative contract.
Cost of Carry
Calculation ⎊ The Cost of Carry for a crypto derivative position quantifies the net expense incurred from holding the underlying asset until the contract's expiration or settlement date.