At the moment where I have the choice to enter the Matrix I weight the costs and benefits of doing so. If the cost of, say, not contributing to the improvement of humankind is worse than the benefit of the hedonistic pleasure I'll receive then it is entirely rational to not enter the Matrix. If I were to enter the Matrix then I may believe that I've helped improve humanity, but at the moment where I'm making the choice, that fact weighs only on the hedonistic benefit side of the equation. The cost of not bettering humanity remains spite of any possible future delusions I may hold.