Many customers/clients don't even want accurate estimates. Given the choice between an accurate estimate of $x, and a competing estimate of $0.75x with later s

Many customers/clients don't even want accurate estimates. Given the choice between an accurate estimate of $x, and a competing estimate of $0.75x with later surprises and deadline stress and renegotiations to pay another $0.35x for "phase 2" which gets the product up to what they originally wanted, especially when the business relationship has "bonded" in a way where it's all rah-rah, go-team, we're-in-this-together... clients will go for the latter path way more often than they should. Part of the reason estimates are inaccurate is because there's that business disincentive to be accurate.