Don't forget that a float's advantage is compactness, portability, simplicity and hands free manoeuvering where both hands are available for holding the fishing rod.
Without the "hands free element, either a kayak or a pontoon becomes a more efficient small water fishing craft. Both have superior water speed and range than a float tube, but the need to put the rod in a rest reduces their fishing value significantly.
Oars on a tube:
add bulk when put away
necessitate "rod out of hands" fishing style which is a far less efficient way to fish
So yes they are an intriguing idea. But the same reason for choosing a tube with oars also tilts the balance for choice of a pontoon/sit-on-top kayak at time of purchase in preference to the tube.
i do agree though that it will add some weight and also take away some space. but for someone who wants to cover more water, i believe the pros outweighs the cons.
what i am saying is: it really depends on your objectives and needs.
for me, it is very suitable since, my needs are to cover as much grounds as possible in an area which i need much better portability than carrying a pontoon. this stuff suits me just fine.
that being said, it may or may not be suitable for other tubers. so yah... all tubers gotta look at how it suits his own requirements.