In the kind of sucked up relationships our current culture often breeds... no, marriage isn't going to help anything.
But KontrollerX, despite my respect for your often dead-on analysis, this one you're slightly more wrong than right. Stastistically at least. My dad is a psychologist, and digging through some papers on his desk one day I ran into an article from one of the psych journals that did a study on this, and it turns out that married people still rate their sex lives on both a greater frequency and satisfaction scale than single people, live ins, etc. If you really care, I can probably get the cite for you.
Obviously what you're pointing out happens. Sadly it happens a lot. But there certainly are a lot of marriages where a LOT of sex is happening quite regularly. I know quite a few couples who didn't have ANY sex before they got married, and *** like rabbits now. One girl I've known for awhile randomly IM's me one day and says "omg, my husband is coming home next in 3 days!!! I can't wait to have sex!" I told her 1) TMI, and 2) You're a crazy ***** (jokingly.)
But yeah, it does happen.