I can't speak for other countries, but at least when it comes to programming, it's really easy to become a freelancer here in The Netherlands.
In less than a day you can register your business, get a business bank account (+ working card!), and send an invoice to your 'employer'. For less than a hundred 'bucks'. Once a year it gets a little more complicated when you have to do your finances, which can trivially be outsourced to an accountant. I know plenty of people (perhaps especially programmers) who do their finances themselves though. For freelancers, and especially programmers, it's (apparently) not that complicated.
Going through this for just one month before you're hired is perhaps still a bit too much of a hassle, but you only really have to do this once and you can then use your freelancer status every time you switch jobs.
I don't know much about the legal aspect of all this though.
It's not just the paperwork; is that you then have to calculate your rates, your holidays, your pension payments and so on. You get a number wrong and you don't go on holiday that year; you get a number wrong, and on the month you have to pay your taxes you don't have cash to feed your kids. And all this before we even get to the issue of finding and maintaining business relationships, without which again your kids go hungry.
In contrast, regular employees don't have to do any of that - they know they will get a paycheck around X every month, will have Y days off work and (if the company is not run by crooks and/or nosedives) when s/he retires she'll have a pension worth Z. It's a completely different mindset, even before you get to the bureaucratic side of things.
In less than a day you can register your business, get a business bank account (+ working card!), and send an invoice to your 'employer'. For less than a hundred 'bucks'. Once a year it gets a little more complicated when you have to do your finances, which can trivially be outsourced to an accountant. I know plenty of people (perhaps especially programmers) who do their finances themselves though. For freelancers, and especially programmers, it's (apparently) not that complicated.
Going through this for just one month before you're hired is perhaps still a bit too much of a hassle, but you only really have to do this once and you can then use your freelancer status every time you switch jobs.
I don't know much about the legal aspect of all this though.