How do you know that "a carbon layer" is not enough?
I think some people have used cheap one-stage air purifiers and are not impressed at air filtering. Makes it get a bad rap. I think it is up to the due diligence of the owner to research the product they are purchasing when they get an air purifier.
There are plenty of options that include a carbon filter that would be reliable to handle VOCs within the expected life of the filter but knock-off aftermarket filters can skimp on compounds. Filters can be an expense but it is insurance to good quality air in my mind and worth the yearly cost. A multi-filter air purifier utilizing HEPA, active carbon, pre-filter and maybe a pleated layer is ideal. I hear some systems are utilizing UV light filtering as well.
My house is old and on a boiler system, I wish I could get whole house air filtration but I settle on bedrooms getting running machines.