There are 2 different uses of "contractor":
(1) contractor : officiall IRS tax classification of 1099 independent contractor
(2) "contractor" : a W-2 employee of a "temp agency" or "staffing agency" or "bodyshop" that is sent to a client company (such as Google) needing contingent workers. Adecco[1] is an example of a staffing company that sends people to Google. These temp agencies with workers classified as W-2 employees act as legal cover to "avoid repeating Microsoft lawsuits". From Google's perspective, these Adecco employees are "contractors".
If the above working arrangement looks convoluted with the economic inefficiencies of paying for an extra middleman (the temp agencies), it is. But it cleverly avoids the IRS claiming, "Hey Google, your so-called contractors are misclassified and should be employees!" ... and Google can say, "They already are employees! They're Adecco employees!"
The "1099 real contractor" is not as common as "fake-contractor-but-really-somebody-elses-W2-employee" ... because the "1099 contractors" won their lawsuit against Microsoft.
These laws do not protect workers, they protect entrenched wealthy body shops.
In effect, this scares companies so much that it is very difficult to get hired as a 1099 contractor as a programmer/engineer. The vast majority of companies will require you to be a W-2 employee of some other company (which will be the "staffing agency" or "bodyshop" or "temp agency").
One programmer was driven to fly his aircraft into an IRS building due to this issue.
I get why 1099s can’t but what’s the deal with the other, now more common situation?
And the ruling makes it clear that it’s based on the actual on the ground reality, which is why vendors get pulled in the same way.
If the main company is the one giving the vendors employees their direction, managing them, setting hours explicitly, they get included in all hands, etc. then the main company is also on the hook for being their actual employer as far as benefits, taxes, etc. go.
So there needs to be a clear delineation at all times, or bad things happen to the primary company regarding costs.
If you are setting their hours, bossing them around and/or providing equipment they are not a contractor they are an employee. This is the law in 100% of the United States.