"Possibly" two reasons. Doesn't seem like you've given this much thought on such a supremely important issue. But no real surprise. Most people don't. They just go by gut feeling.
I'm going to gloss over the first two arguments because one is so vapid and shallow and the other is simply wrong. The idea that two people should enter into such a sacred union so that they can squeeze a few more shekels out a legit business that exist to make a profit. Something that for some reason bothers people. They want to make money doing whatever they do but if anybody else does it are greedy and exploitive. It really diminishes a union if one of the reasons you get married is to get someone else to pay your health insurance. And the abuse is endless. I can marry my buddy just to help him out and get health insurance. Of maybe even charge him for marrying him so we can both make a profit.
And it's simply not true that you can't have anybody you want visiting you in the hospital. I did it. Both my parents did it. They had non relatives visiting them without any prior approval. That rule is selectively enforced such as if your are a celebrity or VIP so you don't have every dredge in society lining up outside your room.
Now your last reason I think deserves a bit more consideration. Not because it's a strong argument but because it's so frequently use.
If love is the litmus test what's to prevent someone, what arguments can you make, from marrying their uncle, sister or brother? Hell, nowadays people are talking about marrying their cats. Should we permit a legal binding union of two brothers? A mother and her son? A granny and her cat?
When gays talk about rights, having equal rights and the same rights as hetros, they obfuscate the issue. They don't want equal rights. They already had them. They want special rights. They want to redefine a union and institution that have existed throughout human history. And all because they claim they are in love?
1. Define "they"? Heterosexuals who marry and who have health insurance benefits can have 2 party or family coverage. Although, many times there is an added cost. Throughout our marriage, one of us, (usually my wife) had double (primary and secondary) coverage as each of our employers provided health insurance benefits. -Perfectly legal and it saved us a lot in medical costs.
2. Visiting rights are more complicated than you suggest. According to law, you are correct. However some hospitals require non-family visitors, be put on an approved list by the patient. A patient who is not conscious is unable to do this.
http://www.unmarried.org/health-care/hospital-rights/;
https://www.aclu.org/other/faq-access-patient-information-friends-and-familyIt is an excellent idea to have POLST information posted in an obvious place in your home (recommend refrigerator) and on file with your GP.
3. Marrying one's cat goes too far. I think there should be no marriage licensing, a detailed legal contract between two people makes more sense. It would be like a prenuptial legal contract that takes effect as soon as it is signed by both parties.
Weddings are social and often religious event which should be optional. No one should be forced to perform them or provide other services for the couple, such as flowers and cakes. IMO.
4. There is nothing obfuscating about about the meaning of equal rights. Equal rights are equal rights plain and simple, regardless of who requests them.
If love were a condition of marriage legal or otherwise, many more folks would be single. Whether heterosexual or whatever, a lot of folks would not know love if it 'bit them in the ass'. People marry for a variety of reasons, some good and some not so good.
