I simple don't understand why the rules should allow tacking one (or more) distinct, unrelated items onto a bill.
It's been around for a long, long time and used for attaching such things as "pork barrel projects", unpopular laws, and every popular "special interest tax rates" whereby a company's tax rate (or individual for that matter) are granted. For companies it's usually something like "a company that incorporated at 11:15 am on Feb. 20, 1975 in (city, state) is granted a tax rate of XX%. It's surprising to see the crap tucked into bills for "important stuff" by CongresCritters.