I bought a 4x4 and I'm now driving a 2010 B4000 4x4 with brand new 245/75-16 Blizzak DMV-1's after 16 years of 2wd (b3000) with weight in the back every winter and I drove my truck for 6 weeks with no weight to see if I liked it... I didn't. Weight in the back helps balance for turning, handling, control, braking and acceleration in slippery conditions in 4x4 and 2wd.
20kg x 6 salt bags so 265lbs over the wheels in back and I'm much happier with my truck.
If your 4x4 and haven't tried it find a snow covered parking lot and pick / make a course around the lot and run it with and without weight in the back. You might find you can make it around much faster with the weight in the back. This doesn't mean you should be driving faster on the road just use that extra potential for an extra margin of safety.
Do you 100% need the weight? not a chance but why would anyone chose to drive a less capable vehicle when improvement is so cheap and easy.
Sure a good driver can manage the conditions to be just fine with no weight and even poor tires but the question for me is always the same... why would you want to drive a less capable truck? Driving in terrible winter conditions is like off-roading... it's just too fun for me to not want to enjoy it to the maximum