Why Sterility test require 14 days of long incubation time?

Sterility testing is the method to check viable contamination (bacteria, fungus, spores etc.) in the product. This testing is very important but it is time consuming. Once you tested the product, it require 14 days of long incubation time.As we know that bacteria require 3-5 days for the growth and fungus require 5-7 days for growth then why sterility incubation require 14 days? Sterile products are manufactured in aseptic environment and that environment must be suitable for the sterile product manufacturing. We perform environmental monitoring to check viable contamination in the area and to control viable contamination we perform disinfection, sanitization and fogging in the area. Personnel are also involved in the aseptic manufacturing activities and in aseptic area personnel are the main source of product contamination. Sterility testing require 14 days of long incubation time because there are some bacteria which are very slow growing like Propionibacterium acne. P.acne is gram positive, rod shaped, slow growing bacteria which is found in the acne of humans. This bacteria is associated with the humans and very slow growing and it could be the source of product contamination. So, for the recovery of these type of slow growing microorganisms, 14 days are enough to support the growth of these slow growing microorganisms if present in the product. Another reason is that in aseptic environment microorganisms could be in damaged or in injured form so it require long time for the recovery of these microorganisms in media. That's why sterility testing require 14 days of long incubation time