I've seen several of these rubber gaskets (Isuzu officially calls "Glass Run"), and IMHO the rubber gasket/track/run itself is not getting worn down.
I've heard of, but haven't seen any with a "split" of any kind involving the rubber channel.
I believe it's a combination of 3 factors:
1) Rubber gets dry and doesn't allow the glass to slide easily thus causing glass to bind and struggle to go up. (So lubrication helps). I "think" because the rubber channel gets dried out, it causes glass to kind of stick to it, causing it to get ripped and torn up as glass goes up/pdown.
2) The metal channel (see my post #29) is too narrow, causing rubber gasket to be squeezed into the channel, and therefore causing more friction on both sides of glass,
3) The metal channel is pushing rearward, thus applying more pressure on the forward EDGE of the glass.
So that's why widening the channel as well as moving the vertical channel a little forward helps relieve pressure on the glass, allowing it to slide easier.
**** I don't know if any of this affects the TILT issue, as mine has never had that problem ****
I have a used glass run from a '99, I can take detailed pics of channel to see if it's showing any wear.