The mistake I see my fellow engineers make is assuming they're not disposable because they're full time, or that the axe won't eventually turn on them.
Contractor output is frequently technically shoddy or lazy; their reports are riddled with grammatical mistakes and frequently difficult to understand; and there is no way that they could take point when interfacing with a customer as their English skills simply aren't good enough.
But the quality of the contractors is ultimately irrelevant because we're talking about workplace protections and benefits. You SHOULD be blaming your company instead for taking cost saving measures that impact the rest of your organization. If your company is working with contractors that are core to your business then they should be treated the same as your employees. And we should be eliminating the middle area where companies want to treat contractors as lesser employees so they can pay them less for the same work.