55% who want it to be more strict is still more than the 45% who don't want it so or are undecided. If this were a voting matter, picking up 15 percentage points means nothing if it still doesn't take you past your opponent's percentage.
And the whole point of a constitutionally limited republic is so that 55% cannot dictate to the other 45% unless they can successfully argue that what they want is right rather than merely popular.
You get the same number of votes every election, regardless of how many facts you know or opinions you hold. We really don't want to live in a society where 51 idiots can overrule 49 geniuses. (Insert insult against congresspersons here.)
The polling numbers only tell the more spineless representatives how much risk they will take with regard to reelection if they choose to act with due consideration of all parties' interests rather than pander to their base or log-roll with their peers.
In the early 1990s, ~70% believed gun laws should be more strict. Today it's ~55%. It's unchanged from ten years ago.
It's extremely clear that American's aren't, and haven't been, in a hurry to further restrict guns in any major way.