Why would you dry cigars in humidor?

I think you are referring to "dry box". 70% is the recommended humidity level for storage . The problem is for some cigars that is not the best humidity for smoking... some will barely smoke at 70%. The idea is you have two humidors, one for long term storage at 70% & one with no source of humidity. Depending on your smoking needs you keep a few in the "dry box" which will keep them protected and let the humidity level down gradually. There are as many opinions on this as there is smokers... I smoke everything I buy so I try to keep my humidor at 67 to 68%. It is helpful to have 2 separate humidors. If you have a humidity spike, you will still have something ready to smoke. Part of the intrigue is the science of the "perfect" smoke... enjoy.