Free parties as in you paid for alcohol and gave it to everyone? Typically, when I'm home in the summer and hangout with high school friends (mostly at UVM), someone will go to the liquor store, get kegs/handles/whatever, and then we all split the cost so that he isn't out $100+. The alternative is to do a rotation. Social dues for greek life (many clubs do this as well, at least at my school) essentially is just a more organized way of doing this. Everyone pays once (typically at the start of the semester), and then this money is pooled and used to plan parties for the entire semester. Renting out a bar for example, can cost $1000+, more if you want open bar. So instead of everyone paying $5 at one party, and $20+ at bar events, we pay once. Not all dues are social, some cover things like living in the house, or even meal plans. Also, some people can't afford dues, but they are not excluded. There are a number of opportunities for them to contribute in other ways, or exceptions can be made for certain situations.
As far as opening parties, the general mentality is that if you paid for it, why would you give it away for free? If a party is organized between two groups, it can also be seen as disrespectful to open it to anyone.
I'm not gonna lie, certain people can be tools, but this is not exclusive to greek life. Take any large group of males, get them drunk, and you are bound to see a few bad apples. The exclusivity can also quickly lead to elitist attitudes. I think that in many situations though, greek life is simply the larger social presence (compared to sports/clubs), and therefore you will see more tools.
As far as the last part, the stories you hear on the news are sometimes blown out of proportion, and they represent a minority. I personally was never forced to do anything I would consider degrading, but I do know it exists in some places. It also exists among sports teams and other clubs. For example, a student in Florida was killed as a direct result of hazing done by the band a few years ago.
http://www.orlandosentinel.com/news/famu-hazing-band/
As far as networking, good for you on getting a job. Networking isn't a requirement for a job, but it can be very helpful in certain situations, and I would never say that having more employment opportunities or even connections is a bad thing.
You do make fair points, and every school is different, but a lot of the time a few bad apples can give the whole system a bad name. I acknowledge that these bad apples still exist, but I don't think its fair to generalize on the actions of a few.