Every person spends their money differently, and every parent also raises their children differently. Your parents may think that it's unnecessary to give you more money and want you to value how you spend your time and your money. It's a lesson that some people never learn, and when they are on their own, they spend too much money and throw themselves into debt. You can consider talking to your parents... who knows, maybe you can even ask for an allowance. You can decide how you want to spend it... it's something to consider, but if it's really bothering you, then maybe you should bring it up. Maybe they can explain why they do these things, or maybe they'll be a bit more lenient.
And if that doesn't work, consider working. At your age, you may not be able to get a very formal job, but when I was 12, I was babysitting. And at 14, I had would make about 20 dollars an hour tutoring people. People need dog walkers or people to rake their leaves... it's something to consider. If you want some spending money on the side, then maybe you can get some work that will let you make that money.
I'm going to spend the next bit to explain some costs that maybe you don't see your parents are having. Maybe your parents are "misers" as you like to call them... but maybe they have some other costs that you've never realized. So here are some general costs that you may want to consider.
Now, you said that they get around 8k per month? Is that individual or together? Do you know the rent on this "small apartment"? Depending on the area, your parents could easily be paying 2000 a month on this building. You have internet at your home, what about cable and phone? You also have all the utilities that need to be paid. And if you turn on the heater, then that increases costs. I live with two other people... and for just three of us, in the winter, we can pay around 4-500 dollars every two months. Since you're a family of six, let's just say that your parents may pay about 300 dollars per month on these bills. If any of you have cell phones, that can add up to another 100 per month. Do they have cars? Have they paid them off? How far do they drive? Insurance can be about 50-100 dollars per car, then there's gas prices, etc.
Also, are you aware if either of your parents have debt? Take school debt, for example. I know someone that has to be 300 dollars a month just on school loans alone... and that continually gains interest as well. Maybe they have general debt from before, such as on credit cards and the like. I don't know how long your parents have had these jobs, but maybe it hasn't been long enough to cover these debt payments.
Also, you said they have an 8K salary. You are aware of taxes, correct? My sister gets about 5K per month, but she has to pay over 1K per month on the taxes alone. So even though their salary is 8K, depending on how they claimed their taxes, they are making LESS than that each month.
Also... there are four kids? And in about 4 years, you'll be at the point where you'll be looking into colleges, if you decide to go. College is a HUGE expense, and maybe your parents wish to save up for the future of their four children. Don't forget food as well, that is a very big expense... and things like toilet paper, paper towels, etc... all cost money.
These are all just thoughts... I don't know what your parents are actually like, but I just thought that maybe you could benefit from knowing that things add up. And.. they work hard, so they may not be willing to spend the money that they work on on these things.