A marriage license is a legal binding contract. If it was "just a piece of paper," you could tear it up and be divorced, but you can't, you need a lawyer.
If it was "just a piece of paper," then why does it give you so many benefits? You can use your spouse's insurance, you can get family rates/discounts, you can file jointly for taxes, getting more back, etc. There is a whole list you can read here.
If it was "just piece of paper," why do so many homosexuals want it? Obviously it must be more than "just a piece of paper."
There are also some people who are together, have kids, and just don't get married. They are happy where they are. I don't think I will ever understand this. You get so many benefits from being seen legally as a couple, so why not just get married? You love each other, you don't plan on leaving each other, so why not? It makes legal matters less complicated. For instance, If you die, your spouse will automatically get your life insurance and vice versa. If you aren't married, this could be difficult unless you have a Will and it states you want your money to go to your partner, otherwise it defaults to going to your parents or your kids.
It is a shame how marriage today is seen either as nothing, just a piece of paper, or a show: "Everyone's doing it, so I need to have a wedding." It's rare to find a marriage that lasts till "death do us part" anymore. People either rush in or decide not to at all.
To us, marriage isn't just a piece of paper or a contract, it's a promise, it's unconditional love. We are dedicated to each other. We may have only been married for two years now, but we've been together for a total of five. Some would still say that's not very long, but I think we have the right idea. After all, our marriage has lasted longer than some celebrities and others we know.