The classic example is the shell, if it's in a chroot say there's not a lot for you to execute. However the shell itself remains pledged.

Pledges must reflect the capabilities of a program. Yes the "proc" and "exec" pledge promises are powerful but they can be constrained by their environment such as chroots or calls to unveil.

As an aside if you have very good knowledge of what a pledged program executes you can opt into setting up pledge for it ahead of time in the form of execpromises.