[loceng]

Creating a buffer for the unexpected allows for pleasant surprise - or possibly magic.

[xwdv]

Also known as lowering your expectations.

[mandelbrotwurst]

That’s one way of looking at it. It could also be described as being realistic - there are always “unknown unknowns” and all else equal, no matter how motivated and capable your team, estimates that consider this will be more accurate than those that do not.

[hinkley]

Or not painting yourself into a corner.

[contravariant]

Mostly everyone elses, but yeah.