A property tax lien is tied to the title of the property - many counties/states auction the tax lien but not the house (then you pay the person holding the lien or they can force a sale (but getting clear title is another story). Many people buy property tax liens as an investment (guaranteed to pay off at some point- pretty safe.). An Income tax (state or fed) can trump any mortgage in a sale and the IRS will force a sale of your home especially if there is equity in it and even if there isn't.
If you are selling a house with a property tax lien against it - it has to be paid in order to pass clear title. But an unpaid income tax lien can take 1st position over a mortgage (existing or new) and lenders loathe that.