Well, that's the thing. There are a whole bunch of different types of hammers. For most hand-nailing jobs and striking nail sets I generally prefer my 16-ounce straight-claw hammer; but occasionally if I'm just doing a little rough work I'll use the curved-claw one, which has poorer balance but makes it easier to pull nails. (If I'm using the straight-claw, I'm generally pulling nails with nippers, which are the proper tool for the job, or with a flat bar if I'm doing demolition, or with a cat's-paw if I need to dig them out from below the surface of the wood.)
The straight-claw hammer also has that T-cut in the top of the head with a magnet, used for one-handed nail-starting. (Yes, you can do the same by holding the nail to the face or cheek with your hand and smacking it into the wood, but you can't get a good swing that way.) That's a useful innovation that came out, what, 20 or 30 years ago?
If I did much framing with a hammer, rather than using the air nailer, I'd have a framing hammer, probably a 22-ounce with a waffle-pattern face and a straight claw. Significantly different from the 16-ounce smooth-face one.
I have a short-handled 5-pound sledge and a long-handled 10-pound one. Same design, different sizes, quite different applications.
I have three different sizes of ball-peen hammers, for various tasks.
I have rubber-headed and wooden-headed mallets. I have a dead-blow mallet. I have a double-faced tack hammer, with a slotted head on one side. I have a couple of pickaxes, which are hammers — or are they?
I've seen many debates over hammer handles over the years. Many professionals prefer a plain wooden handle, but some like fiberglass and some like padded steel. My father for many years used an old 16-ounce straight-claw nailing hammer that had a handle made of leather disks (elliptical, actually) stacked on a steel shaft; I don't know that I've ever seen another like it. There are those framing hammers with eccentric shafts that are popular these days.
In fact we have quite a large array of hammer designs. The principle remains the same, but the design and implementation have most definitely seen extensive innovation and variation.