I think the problem is that most people, especially non-engineers, are over-selling and over-promising all the time. Being honest about risks, issues, and short-comings makes a project or product look bad in comparison.

The most feasible way to get X done is saying "X is a great option, the risks are managable, and it's fairly quick". Then, it will unexpectedly take a bit longer, plus some unforeseen trade-offs will need to be made.