Holding tank chemicals

I've been in RV's where the owners did not use chemicals, and believe me, the smell is in the bathroom. Perhaps those of you who insist that you don't need them have just grown accustomed to the air and don't notice it anymore?

I don't get all the anti-additive sentiment here. We camp without hookups and need something to hold the black tank over for multiple days until we dump & go. I use Thetford Aqua-Kem Toss Ins. They do a great job and I never smell anything funky. Easy as pie.