I see several reasons to purchase a craft like this. If you are a shallow water or a river fisherman, being able to cover some distance on the water can be important. In a river, paddling a kayak against the current while it can be done, is not always easy. Being able to motor upstream and float back to your put in place is a great advantage. Having a jet motor and being able to travel the shallows where prop boats can't go is also huge.
As someone who regularly floats rivers, being able to get off the water quickly when a storm comes up is important.
I can defend a purchase like this because I just purchased a boat that does a lot of the same things except that it can hold 2 persons. Mine is like a jet powered canoe on steroids.
It's light, only weighs 250lbs (without the motor). 16ft long, 4ft wide. Unlike a kayak, I have a trolling motor and oars. I can run shallow rivers, and I won't need another car to shuttle me. I can get 10 miles up or down stream in 20 minutes. That's a long way to try and paddle especially going upstream. To get where you want to go you have to have the right craft. An $80,000 bass boat can't go where this boat (or a jet kayak) can go. I paid more for just the jet motor on my boat than that entire jet kayak costs.
For someone who wants to fish small lakes, the jet kayak is not for you. But for a flats or a river fisherman, It might be just the right tool for the job.
My river fishing craft. A Towee, Rivermaster with a Tohatsu jet motor