right on Don, couldn't have said it better myself, the handles do usually have a slight upwards curve, meaning of course as you mentioned, a nice contact angle for the cutting edge, and I might add letting you stand a little straighter to obtain that nice contact cutting angle
At UCV we have an extensive collection of hewing axes in storage some with handles and some without. Both types that were still attached exhibited both straight (no upward sweep) and some with a pronounced upward sweep
It seems to me that the straighter ones were replacements, but then not certain--just an educated guess--the nicely curved to me seemed of a better quality, and were hand done for sure--you can pick out the store bought ones, machines certainly have no feelings, and only deal with offsets and angles--even the size and cross section of the handles are manufactured from a pattern you can tell
I personally like the handle to take a gentle sweep out and gently upwards as it exits the eye of the axe--I like a small notch in the end of the handle for my little finger to snuggle into
Man can you sure get used to a custom made handle it is really scary if you break one you are really used to and have to create and hang one as a replacement--not a good feeling--trying to get that control back that seemed so easy with the old handle
only broke one in my career, trying to sever a large red pine knot, and made the mistake of coming down hard with the heel of the blade---not a good thing to have done should have known better--but as they say hind sight is better than fore sight