I think it is more common for the umbrella union orgs to focus on industries either with high barriers to entry (like nursing) or huge employers, because they are going company-by-company & it's just more efficient. On the opposite end of the spectrum, trade unions are more likely to serve people who change jobs ever couple of years and where most of the learning happens on the job. They tend to be run by & for people actually in the profession and can cross company boundaries.

Trade guilds will do things like specify minimum wages, but most of their members end up paid more than that. They'll specify minimum safety standards, but also support people on specific job sites that want or need additional protection to make that particular job safe. It isn't the same kind of one-size-fits-all approach you may be used to from Detroit auto plants.

There are advantages for employers too: they know that people in the guild are held to certain professional standards, for example. When retirement programs or health care are managed through the guild, workers can take the benefits with them to their next job, and small employers don't get taken for a ride. And employers can benefit from the steady influx of newly-trained workers who have been taught up to the standards the trade feels are important to meet.

Just look at the people in this thread who think it is "drastic" to have a lawyer look at our employment contracts: we may have individual leverage, but we aren't necessarily able to use it to make our working conditions better, or even to ensure the software we build is reliable and safe.