You can pull that kind of stunt when you have, or are running for, the executive; but if you want to get your veto-proof supermajorities working towards one end in concert, everyone needs to have run on - and with - the same playbook. Otherwise, you’re spending so much time trying to placate the squishies in your own caucus to get them onto the team that you’ll lose time and initiative. As much of an SOB as Newt Gingrich is, he had the right idea on how to get a legislative chamber moving in the same direction.
The mandate keeps your own troops in line, because you know the Republican Noise Machine will do its best to pick them off one by one.
FWIW, that was just an example. Sub in whatever large-scale controversial issue you like- pro choice legislation, pro-environment legislation, well-funded Mars missions, etc…
When you have a super-majority, you are beholden to members from states and districts normally controlled by the other party. Without knowing what sort of Democrats the newly elected Democrats might be, it is impossible to say whether they could be whipped by leadership.