I still remember that in 2010, the approval rating of US Congress was 10%, and yet 90% of incumbents was reelected. How the hell is that possible?
Maybe you love your representative and Senator(s) but your party is in the minority. So, you don't approve of Congress.
Maybe ditto on the liking your reps, but Congress is always doing really stupid shit even when your side's in charge (like the goddamn own-goal "debt ceiling" bullshit) simply because they can't rally enough support to make that junk stop, so you don't approve of Congress. Or maybe your side controls both houses and the Presidency but still can't do jack-shit because of Senate rules, or because some other Senator or two (not yours) in your preferred party like playing both sides to advance their state's interests at the expense of everyone else—so you don't approve of Congress.
Maybe you like your reps and your side is in charge but you've really taken anti-politician stand-up jokes to heart, or follow media that highlights and exaggerates all the stuff you hate about reps on the "other side" even when yours is in charge, so you tick the "disapprove" box.
And so on.
Personally I also find it bizarre system where the majority vote of the other 49 states tells your state what to do, under federal law, particularly in wholly intrastate matters.
I'm sure states would love to just take that money in directly, but the federal government gets first dibs and states complete with each other on the remaining taxation. For instance, Florida is not just a popular retirement spot for the weather -- it also has zero income tax and a property tax with capped year-over-year growth.