Pilots on the job have plenty of leverage. Without them the motor stops turning. Those rookies can't fly the jet all by themselves. And just imagine if all those senior training instructors all came down with the flu at the same time..
Kidding aside, of course seniority is difficult to give up. But there are plenty of ways to put up the good fight without quitting. But keep sending more excuses to sit on your hands...

You keep using the contract as an excuse to accept things how they are, yet the company has gone outside the contract to pay newhires. Maybe if you stop whining like a little (insert unkind words here) and put some work in, the company could go outside the contract to pay you some of that extra money they're throwing at those all-important newbies..