For some internal contests (like team forming or ranking contest of a university), often you might need the contest to be accessible by only those who have link to it. Otherwise, filtering the ranklist becomes very troublesome too.
So an option to share a contest via link would be very helpful.
The main objective here is that a group of users (who have the link) can participate in the contest while the manager does/can not know all their usernames (so can’t invite them all manually).
This requirement can be made with a password system for contest too, like in VJudge.