A Ricasso is an unsharpened length of blade just above the guard or handle on a knife, dagger, sword, or bayonet. Blades designed this way appear at many periods in history in many parts of the world and date back to at least the Bronze Age; essentially, as long as humans have shaped cutting tools from metals.
There were many reasons to make a blade with a ricasso, and in Europe, later longswords, claymores, rapiers and other lengthy swords often had this feature. One very simple influence presently and historically is fashion, which often answers this question for blades where the presence or lack of a ricasso has no effect on how it is used . Leaving a ricasso can also save the blade maker's time - a section of blade that would not be used given the purpose of the piece does not have to be shaped and sharpened. In many cases however, they are quite functional.
Historically, ricassos were commonly present on medieval and early Renaissance swords. The basic function was to allow the wielder to place their index finger above the crossguard, which potentially allowed for greater grip strength and torque. This technique was a factor in the evolution of compound hilts which are iconic of rapiers and other Renaissance swords, as the compound hilt allows a ricasso grip while still protecting the hand.
I'm walking unknown territory, where the sun's not shining
There's nothing golden about Golden Lane
The smoke is heavy in my lungs and the adverts are working
I just can't sell for who or what I am
I don't wanna miss out on anything
At the same time I feel the need to retreat
Everything is temporary these days
Might as well go out for a third night in a row
Should I give my money to a good cause or save for a holiday?
In a couple of months I could be in paradise
But the girl at the bar is well nice and she's looking over
It's only right that I get the next round in
I don't wanna miss out on anything
At the same time I feel the need to retreat
Everything is temporary these days
Might as well go out for a fifth night in a row
Walk home, come down, retreat to sleep
Wake up, go out again, repeat
Walk home, come down, retreat to sleep
Hook up, again this time, next week
Walk home, come down, retreat to sleep
Wake up, go out again, repeat
Walk home, come down, retreat to sleep
Hook up, again this time, next week
I don't wanna miss out on anything
At the same time I feel the need to retreat
Everything is temporary these days
Might as well go out for a fifth night in a row
Walk home, come down, retreat to sleep
Wake up, go out again, repeat
Walk home, come down, retreat to sleep
Hook up, again this time, next week
Walk home, come down, retreat to sleep
Walk home, come down, retreat to sleep
Walk home, come down, retreat to sleep