My guess is because of the opportunity cost. If you hire the wrong person you end up firing 3 months later, you likely missed your chance to hire a better candi

My guess is because of the opportunity cost. If you hire the wrong person you end up firing 3 months later, you likely missed your chance to hire a better candidate (who is unlikely to apply again to work for you) and you will need to restart the whole expensive hiring process again (even a more lightweight process is expensive in employee time, maybe paying recruiters and job listing sites, etc). Also onboarding is expensive: even an experienced developer who has all the skills you need still has to learn your codebase, processes, business logic etc. while drawing a salary, and all that goes to waste if they leave before they can start becoming a net positive to your company.