Gnome, it isn't that the state can't offer protection, it's that the state in this jurisdiction has decided, so far anyway, not to legislate to do so. Other states have legislated to regulate relationships that haven't ever been formally entered into by the parties, which is why de facto law exists. It certainly makes things easier and clearer - even in those jurisdictions - if a formal, legal commitment has been entered into, and the certainty there justifies expecting the parties to take a greater degree of responsibility for the other's welfare going forward... but the balance between certainty and fairness is, IMO, out of whack right now in this country. Allowing some form of commitment that's less all-encompassing than marriage, but still a pro forma contract that can flex as life circumstances alter, seems a good idea. The current system isn't working for large numbers of people, and there are other compromise options that appear to work okay elsewhere, and wouldn't leave large numbers of people so vulnerable to their ex's goodwill.
It's also the case that the banns these days are pointless. Nobody goes and scans the notices at the registry office, and as (unless a lot has changed over the past decade) no central database is kept, it's not that hard to commit bigamy. Publicity was a protection when people lived in smaller communities and moved away from home very little. Nowadays, I don't think it is. If someone wants to commit bigamy and has the sense to be discreet about it, the public nature of marriage isn't likely to be what gets them caught.
OP, maybe Vegas? I mean, it's hard to take an Elvis impersonator marrying you seriously, or a drive thru, you can write your own vows so maybe can skip the wording you most object to, you only need one witness who can be anyone at all, you can get good and drunk first as a way of thumbing your nose at the whole procedure, and I doubt the words are especially sentimental if you don't want them to be... but it'd have the same legal effects.