We issue the coding test if we are unable to determine, from the information provided on a dev's profile, whether or not their skills are a fit for what companies on OfferZen are looking for. There are some companies that expect devs to do a coding assessment as part of the interview process and we want to make sure that devs are ready for this sort of assessment.
Sometimes devs submit profiles that provide enough information on their profile about their coding abilities, such as links to code they've written on Github, online projects or detailed technical descriptions of the coding work they have done or open source projects they're involved in. In such cases we don't ask them to do a coding test.
If one of your colleagues or someone you know was not asked to do a coding test, we would not be able to give you a reason why without their explicit permission.