It's not that simple unfortunately. Some jobs have onboarding, which can last for weeks or even months. While in theory you can figure out if you're being screwed by an employee during onboarding, it would make the entire process a living hell for the employee. So most of the times you go with "they're new, they're learning, let's keep them for X months". If the person decides to slack it off after onboarding than you've just given someone free money for nothing.
Also firing people is not easy everywhere. In EU this is a complex process that can involve unions, trainings etc. While it's mostly a ton of paperwork that you just do it just adds up to spending money on a person who didn't want to work there anyway.
Also firing people is not easy everywhere. In EU this is a complex process that can involve unions, trainings etc. While it's mostly a ton of paperwork that you just do it just adds up to spending money on a person who didn't want to work there anyway.