Then no decision would be made, which is a decision.

When was the last time someone got a supermajority with more than a small number of voters?

Presumably different referenda would be put to a vote if a supermajority were required, namely, ones that are less controversial.

To be fair in some situations where it is not internal political pressure that caused the vote in the first place, large majorities can occur; see the falkland islands referendum on joining argentina