Changing jobs can be a hassle. It means learning new names, potentially changing private healthcare provider, getting new equipment and setup, learning new company politics.
Is it the case you can earn (quite a bit) more as a contractor, compared to full-time employment in NL? At least when I was doing contracting in the UK contracting roles could earn me almost twice as much as permanent roles (without the benefits of course).
The rule I have always followed - though I don't remember where I picked it up - is that contracting should earn you twice as much as your full time salary - that way the risk etc. evens out.
Sadly this is not the case any more; with the new IR35 rules it's common to get a contract that is taxed as salary, except it does not include any benefits. Contracts outside IR35 exist, but they are very rare and pay even less.
I guess this just sounds weird to me. I would have to be pretty desperate to take a 1 year contract from a company that only paid me full-time wage as opposed to a contractors wage.
I have to assume the Netherlands has a lot of developers seeking employment for this to work.
You don't really get any less security than in a country like the U.K, where you can't claim unfair dismissal under two years of service.
As GP says, it's because taking an employee on an indefinite contract is a huge responsibility, and you basically can't fire them unless they set your office on fire.
In France, there's a huge temp ecosystem that was built because of that. Companies don't hire developers, they subcontract to temp agencies for limited time. The advantage for them is if they need to downsize their team, they can simply terminate the contract without risking liability.
The temp agency obviously takes a big cut on the developer's salary, until (at least in my individual experience) the developer decides to fuck off and do contracting directly instead and starts thinking, you know what, the French job market for developers sucks, I should probably send resumes to american companies instead.
You can be fired for basically any reasonable reason though.
I again have a hard time believing you need to set fire to the office before they fire you, don't French companies ever downsize?