A trial period means uncertainty. More specifically, this is another way for an employer to move the risk of hiring back onto the employee. It's the employee

A trial period means uncertainty. More specifically, this is another way for an employer to move the risk of hiring back onto the employee. It's the employee who is going to need to leave their current position for an 'audition'. This is going to put the employee at a disadvantage during negotiations because the employee will likely not have as strong a position compared to have an existing job to fall back on. So unless the 'best' are already unemployed, then this helps the employer reduce their risk, and improve their bargaining power during offer negotiations. As a thought experiment, if you were trying to hire one of the 'best', during negotiations would you prefer if that person was currently employed or currently unemployed? As an employee, I'm glad that generally my BATNA includes staying at my current position (at a minimum).