There has been a mixer that used dust transactions to advertise their service. If that's the case, a block explorer will probably give a hint if you look at the sending address.
It could indeed also be used for tracking, but only if you don't pay attention and let your wallet choose which inputs to use.

You can do this:
Click Settings > Options > Wallet > Enable coin control features.
Then, click Send > Inputs > right mouse button on a dust transaction > Lock unspent.

Or (after enabling coin control features):
When you send a transactions, click Inputs and manually choose what to use (I always do this).

When fees are low, you could send the dust to a burner address (one at a time, each to a different address), or you could even consolidate the dust and your real inputs as long as the fees are lower than the dust is worth. Make sure to only use the dust input and your real input from one address at a time, so you don't link different addresses together (which would reduce your privacy).