We often hear that weight belts will fall off, slip down, hurt the low back and need to be adjusted at depth if diving with a thick wetsuit.
A few people have mentioned elastic rubber belts which address many of these valid complaints.
Wearing 25 or 35 lbs of lead on any belt may not be comfortable. However, many people find a "freedive type" belt very comfortable for a moderate amount of lead - maybe 16 lbs or so.
If a person has only tried a (non-elastic) nylon belt or a pocket belt using shot weights, they might be very surprised about how different a freedive belt feels. As has been mentioned, the rubber belt stays put, has some automatic depth compensation capacity and it can be worn DIFFERENTLY than a scuba belt.
In my experience wearing a lot of lead on a belt that runs across the small of your back can quickly become tiring and uncomfortable. A freedive belt can (and probably should) be worn considerably lower on the hips. The belt is NOT worn across the low back normally, but is draped across the butt. This position tends to reduce back strain and allows the belt to be worn in a variety of positions and it also avoids constraining natural breathing.
This video, which is obviously directed toward freedivers, shows the typical location of the belt which is much lower than "normal". A nylon belt would just slide off in this position.