Another UK example, you effectively have very limited rights until you’ve worked for a company for 2 years. Before then they can fire you for any reason they care to.

Zero hours contracts were never banned in the UK and in fact have been restricted over the years and debate is still ongoing on whether to ban them altogether.

We have diverged significantly from my original point...

> Unions are the only defense that workers have. If there are no unions, the employer can have their pick among desperate job seekers, and give them the lowest wage they can live on.

The major other defense is competition. If there were infinitely many workers then unions would be useless to begin with, because employers would just let them walk out and hire someone else.

Individuals can likewise use the fact that labor is finite to make employers offer more by credibly threatening to work somewhere else. This is trivially shown by all the people who make an above-median wage despite not being in a union.

You do, however, need competition for that, and in turn to not have laws that prop up incumbents and create barriers to entry to new companies (i.e. new prospective employers).

> Those legal protections are easily eroded without unions.

That's very clearly not true based on the situation in Western Europe, in fact legal rights tend to keep increasing even when union membership is decreasing (e.g. UK, France).

As said, jobs and society as a whole have evolved and noone can be elected in government by promising to take away important protections, what they can be elected on is promising to curb union power but that the unions' fault when they abuse striking action.

My understanding is that workers are extremely well protected in Finland and what's happened is only some restrictions on political and solidarity strikes.