Is the US Treasury yield really that important?

For us, it feels like there's no real difference whether a bank offers 3% or 3.5% interest... but when people talk about US Treasuries, they act like the world is ending even if it rises by just 0.1%.
What is the reason for that??
Is it because the scale of the money is different, since 0.1% of hundreds or thousands of trillions is a massive amount?*