You DO NOT HAVE to wipe the device, even if you upgrade from 4.3 to 4.4.2, the firmware from sammobile will NOT wipe your phone. So if you are against wiping then go on, happy flashing. Your data will be intact.
But that being said, I did wipe my device. Why? Cause on previous occasions I have faced issues (some apps force closing etc) without wipe, so from then I always take backup and wipe. Do I like wiping? I absolutely hate it.
Some kids here, who goes by their developer tag also will say there is no need to wipe, well I don't listen to anyone other than me about this case, cause that person haven't faced any problem, I did, and nothing gives you more info than personal experience.
Just my 2cents.