For every company, there is the right number of ISO certifications
... often this number is zero !
... for others it is one or more
This page explores some of the reasons you might want to gain ISO certification(s)
Either as a mandatory requirement from a (potential) customer or just to improve your chances of winning new business, ISO certification will make your company more attractive to customers
Having ISO will give your (existing) customers a level of assurance that your company has been independently assessed by a Certification Body
Taking a process-based approach to your company will help ensure every activity (process) has monitors and measures in place to let you know if the process is working (or not!) - as well as identify how the outputs of process A feed into process B, etc.
Pride in their work
Achieving and maintaining ISO certification(s) can lead to your colleagues taking more pride in their work, helping to ensure they deliver vs their role requirements to ultimately maintain ISO certification
A good, embedded management system, will help drive improvements to process, departments and to the company as a whole - including the bottom line
For most, new business potential is the only reason to go for ISO ... no shame in having this as the key driver for going for ISO (nor for me repeating 'Sales' in the list of reasons!)