Because he is a messy tinkerer, a lousy scrimshaw, incompetent.

I’m less sure than you are that slavery does not have economic benefits, especially in pre-industrial societies. I know, Henry Ford was of that opinion, but there was not a great pre-existing base for buying his mass produced cars.
Moreover, even in industrialised societies, there appears to be lots of benefits in sweat-shops, barely distinguishable from slavery. In other words, if there is a large enough base of consumers that are not slaves, slavery can be economically beneficial (albeit not necessarily for the slaves).
[For all clarity, I’m not defending slavery or sweatshops at all, on the contrary]

Women’s relative lack of physical strength (relative, I know a few women where I would definitely come second best in a physical fight) is a biological given. I’m not sure it is explains all, but it is definitely a ‘basic’.
My point is that this ‘virginity fetish’ is typical of stratified societies. I’m not sure if there are any studies, but prima facie it appears to be so.
It is echoed in the type of gods societies have. From smaller ones, whose gods don’t give a damn about moralisticity, there is a progressive increase in moralisticity of the gods with increasing size of societies. (see Murdock for that). The larger the society, the more stratified the society, broadly speaking. What probably started as a means to keep the peace between not closely related males within a greater society, became a run-away type of model. In really big societies of more than 100.000 or a million that is. Very stratified, often a despot in charge, virginity fetish and moralistic god(s). (see Laura Betzig). Islam (and to a lesser degree other ‘abrahamic religions) are a culmination of that. There is, of course much more, but it is a good background to start with, methinks.

And basically all is because we lack physical strength.

Those who doubt most that humans are just another animal are the ones who are most likely to prove it with their behaviour. (I mean religious conservatives with their opinion of evolution, not men, in case anyone isn’t sure.)

Fear of women becoming more than breeding machines. In stratified societies nubile women are the only asset of poorer families, but they may not be ‘damaged goods’, (so marry them up -that generally means older males-, and marry them early, and see to it they have no sexual pleasure),paternity certainty, fear of infidelity. And of course this sets the rules for the whole of society. The underlying mechanisms are reasonably clear methinks.

By happenstance, just yesterday on the radio, I heard this hour long broadcast by the World Affairs Council with Jack Schenker, former correspondent for the Guardian, on contemporary Egyptian politics.
http://www.worldaffairs.org/media-library/event/1683. I found it quite illuminating.

Yeah. And, we were made by God, but they have the arrogance to think they can improve on their god’s work. If Allah wanted those bits removed, why didn’t he do it?

Yep!

Though the thing is, long-term, slavery is not an economic benefit. Paying workers well is good for he economy. Of course, that will increase the production price, but there will also more people able to afford what you’re selling. That’s why increasing the minimum wage within a particular range benefits the economy.

Also, there has been economic analysis done and if all the women who want to work were allowed to work, the economies of the Middle East and Africa where women are forbidden from working would boom.

I know that’s not where you were going with your comment, which is right on point, but I couldn’t help myself!

I think, at it’s root, it’s about fear too. There’s no other answer that makes sense.