I'll go out on a (pretty thick) limb and say it's because International didn't make many of them.
This because they were pretty expensive new, so sales were low, which leads to scarcity later down the line.
BUT, news flash..... After my 3rd blowout in 2 years, I switched to standard 24.5" commercial wheels and DRW. I've done three trips since the switch, all involving off-road, and I really don't notice a difference. Then again, I'm not pushing the limits. On the other hand, I've never...
Terrastar was the truck that ended International pretty much. The Maxxforce 6.4 (same turd "Powerstroke" on the short lived Ford Superduty of the 2008 to 2010 vintage) is a really bad motor. So bad that International had a factory swap to the 6.7 Cummins for municipal fleets available for a time. Thousands of recalls and warranty claims from cities who had the Terrastar busses. If you could source a Cummins swap kit it could be worth it. But yeah.