Why should this be so?
1. For a start there is little union power around these days to argue otherwise.
2. You have to wait two years now before you get the employee protection you used to get after 6 months.
3. There are plenty of other people waiting in the wings to take your place for a lower fee if you refuse.
4. If you do protest, you can typically kiss promotion goodbye.
5. Employee costs are a significant percentage of total costs and are usually monitored in budgets and reports. It is often a key management performance indicator (like production, wastage, stock levels and so on). So it is in their own promotional interests to keep them as low as possible.
So what's the answer? It depends on your view.
If you need security more than a stunning wage, stay put and argue your case at your annual reviews.
If you want the money, you need to build yourself a glittering CV and jump ship at suitable moments. This may mean volunteering for projects, taking extra responsibility, making suggestions, and sometimes swallowing your pride and compromising your better judgement.
In the lower ranks, getting your way is secondary to getting promoted. The difference you can make is not significant, anyway. The people who can make a difference and can get you promoted are higher up.
Besides, you will eventually have the last laugh when you become more marketable. And nothing annoys your antagonists more than agreeing with them! Be satisfied with that. And make note of No.9 here.
Most of all, keep records of your work, your results and your improvements as evidence for your CV.
Whatever you do, you should realise that it is all a means to an end. Your aim is to build an impressive CV and to back it up with the facts and figures of your proof of capability for your next employer.