It's not a question of our elected MPs being wiser than the electorate. It's a question of what the legislation says, and the Sovreignty of Parliament!

Parliament has always been overwhelmingly pro EU.
All three parties have always been pro EU.
That is why the people demanded a referendum and Cameron had to concede one or UKIP would have taken a huge swathe of their votes and maybe even won the General Election as they had already won the EU election.

Had it been revealed that a legal challenge was likely, UKIP would have promised a binding referendum by changing laws as necessary, and again hammered the big three.