Contract law is based on the fiction that all parties to the contract are equal. While one may quibble over the details, one thing is still true: you need not agree to their terms, and they need not hire you.
Still, there is no sense lumping all "big corporations" together. Some are great, others are nightmares. With every merger / acquisition / restructuring, etc ... what was true of a firm yesterday may not be true today.
Let me give you an example, from here in Reno. Within blocks of each other are two major casinos. Casino "A" has a well earned reputation for playing games, never paying until you sue, trying to get you to reduce the agreed amount bill after the work is done, etc. Casino "P," on the other hand, simply has you present your invoice to the cashier, and you're paid on the spot. Vastly different operations ... though, to an newcomer, they look almost identical from the outside.
A certain supermarket calls me, and the store manager pays me promptly - usually within a few days. A competing chain needed the work done ASAP - then piled on paperwork, and delayed payment, for months afterwards.
You refusal to accept unfair or illegal conditions does have an impact. Rumor has it that one of the "bad guys" I referred to has begun to have trouble, nationwide, finding contractors. I hear that store managers, for the first time, are allowed to directly contract, and pay for, some work. The message is getting through.
Likewise, it is common for me to be asked to wire up some sort of equipment for the installer/manufacturer. Their contracts are usually chock full of requirements that are illegal in Nevada. I take exception, noting this fact, and return them unsigned. Amazingly enough, these firms have no trouble producing a Nevada-compliant contract.