Sit-on-top fishing kayaks have their own imperatives. Because you sit on top they have a higher center of gravity and ,therefore, have to be wider. Width also increases initial stability which is desireable in a boat where the paddler is also a fisherman and has to move around a lot. Fishing kayaks are, generally, on the short side because rotomolding costs increase considerably by the foot. Shorter is cheaper and easier to mold and is lighter. But shorter boats take more effort to paddle. That's a trade-off that has to be made.
Next, fishing kayaks, being rotomolded plastic, can have bottoms that cannot be duplicated in wood or wood composite as far as I can tell. They can have shapes that make the boat as stable as a log raft. Many of the new hulls are advertized showing the occupant standing to cast or dangling his legs over the side or hoisting a 100 lb. tuna up on the deck. There aren't any home built boats that have cracked into that level of stability yet.
One of the newer and flashier fishing "kayak" designs doesn't even look like a kayak. It looks like a short,fat pirogue with an unusual bottom.

: I was curious if anyone has tried making a wider beam and shorter length
: kayak. The kind you see Hobie selling that is used for fishing, etc. I
: have been all over the internet and have seen many traditional style
: builds and instructions. They are beautiful crafts, but i have some
: problems with a 17ft kayak. My first problem is the storage of it. Then
: the stability for fishing as most have a thinner beam. It does not
: necessarily have to be a SOT, but I imagine putting a seat in there that
: would keep me up a little more, hence the wider beam. Also, does anyone do
: a stitch and glue over a frame? I hoping to avoid doing a skin on frame
: for durability and sharp objects.

: Any info would be most appreciated.