The likes of Cella are simple formulations of few ingredients. If ingredients like tallow and shea butter are not sufficiently refined, the base will have an obvious scent. These are then typically masked by adding fragrance.
There will also be more complex formulations that use deodorisers to neutralise the base smell. For example, B&M has ingredients like ricinoleates that serve this purpose.
At the end of the spectrum, you get foams and gels in pressurised cans where $millions of R&D are spent so that their parts are manufactured without much funk to them and any off-scents (like Triethanolamine) masked by fragrances that are carefully engineered to seem ‘hygienic’.
For another illustration, MdC’s Nature is unscented but not scentless. Like so many things in life, raw materials are closer to nature but lack the refinement of processing. Choose your compromise.