Because maybe they support families with their job? Unless they had a ton of savings, parents aren't going to switch jobs with a chance of being unemployed again in 2.5 months. I wouldn't do it and I'm young and single.
Some places have a contract-to-hire approach which is effectively a trial period.
I believe companies fall into two basic structures:
1. agency / consultant model - implement short-term projects, specific tasks, etc. It's easier in this approach to swap employees in and out as new projects start.
2. software product model - the company's entire business model is built around or highly dependent on internal software projects. Institutional knowledge is very important. It's really important to protect the product process and plan for the long-term implementation of strategic vision.
Contract-to-hire works well for #1. But for #2, the overhead and cost of disruption to the core process is too high. Top-tier software products require a relatively smaller number of highly engaged and skilled people to drive projects to an optimal point. These people need to also be directly involved in hiring and onboarding to maintain the culture and high standards. Bad hires can destroy such a team. Thus you end up with the current interview processes as they're efficient and err on the side of rejecting qualified candidates accidentally. If they spent 10x as long on hiring, they could improve the accuracy, but then they wont have as much time to build product which is the key tradeoff involved.
There are a few issues with the scenario you described.
For health and safety, security and tax purposes you would likely not be able to have an extended period of more than a couple of days without some form of contract for that 'trial' period.
If you are an 'established' professional then you most likely would interview for a new job while currently employed. So even in the remote scenario that you would take a couple weeks holiday for a 'trial' you would likely violate the contract with current employer by signing a 'trial' contract.
This would only work for junior positions or for senior professionals who have taken some time away from work. But if you make this a part of your recruitment process, there is the risk that you are discriminating against 'currently employed' candidates.
Other people have mentioned the logistical/financial problems this incurs, but one other important consideration is that you are competing against other companies that don't do the trial-to-hire process and can thus offer more stability. And to be honest, given the state of the software engineer market (in tech-heavy cities), you already get to spend a couple of months trying out a company and then leave if you want. The difference is that the employer isn't similarly able to get rid of you after 3 months (it's too short a time to evaluate a new employee, the company has already invested heavily in onboarding costs, it's much slower to backfill a position than it is for a software engineer to find a new job, etc).
> Why not? If the position isn't a fit for either side after X time on-the-job, that's OK right?
In the US at least, health insurance is a big one.
How are you going to convince me to leave my current job for a 10 week trial period? That right there loses you the set of all people who are currently employed and are fine where they are right now.
Why not? If the position isn't a fit for either side after X time on-the-job, that's OK right?