The age has probably risen as part of some undefined cultural evolution. A hundred years ago they would have scoffed at waiting that long to get married (they weren't allowed to scoff at just plain sex. That absolutely never happened back when everyone was moral
) I had great-great and beyond grandparents that got married at 12 and 14 and 16, and that was the norm.
Much of what we now call childhood (through the high school years) is a fairly new phenomenon. In some cultures, there is almost no such thing. There are places in the world where you are a working stiff by the time you're six. If not at a factory, at least on the farm or in the garden. I read a book by a guy who was a kid in the Soviet Union and by the time he was six his only job was to walk back and forth the mile or two to the nearest well and get buckets of water. He did that all day, every day. I guess he eventually started going to school too, but he still had to get water.
Extended childhood is a luxury. And that probably turned public school into a babysitting business. Which is why you get taught the same damn thing over and over as you move up the grades. Which makes kids bored. Which, when combined with hormones, watching pretty girls on the Disney channel and actually wearing the clothes you see in The Gap causes certain things to happen. Toss in people over 18 getting involved and the capacity for things to turn ugly, by modern standards, increases.
I don't know if they still do it in Utah, but it wasn't that long ago an 86 year old guy from Texas or wherever could go to Utah with his 12 year old girlfriend and her mom (I'm speaking Mormon here) and get married to her legally.
(Oh, heard a great one. Religion is like a movie with sequels. The jewish version is movie I. The christian is movie II. Muslims are movie III. And mormons wrote the fan fiction... Well, I thought it was funny.)
Anyway, people who love rules will come up with stuff like ages of consent. The inconsistency comes from having different people who want rules, not anything logical.
Personally I'm hoping the raise the age to 60. Mostly because I know a couple of hot 59 year olds that would be more fun if they had something to look forward to.
What's that sound I'm hearing. Sounds like a bunch of people are throwing up. Weird...