I'm majoring in HR and I have quite some experience in the field. Your job offer and contract is based on the lowest wage possible according to labor laws and collective agreements. They might be adding little things here and there like a pizza party, but trust me, they want you to do as much as possible for as little as possible.
Why do so many people allow this? Because it happens indirectly via a contract. Your boss isn't directly coming up to you like “listen buddy, I found this is the lowest I'm allowed to pay you, you're probably fine with it right?”. But he basically is telling this to you through your contract.
How do you prevent this? Don't accept it. Negotiate your salary, PTO, and other secondary stuff. You won't believe how assertive some people at key positions can be. We were recruiting a new director who wanted a leased car on the business. They said that it's not possible. Well what do you know, a few weeks later we were done negotiating and she got it. It wasn't possible you say?
I'm not saying that you should ask for thousands above their pay offer, but know that contracts are negotiations. If you don't negotiate you're allowing your boss to walk all over you. Don't let that happen.