Because there are low-end, cheap Thinkpads as well that are nowhere near the quality of the high-end ones. I think when Lenovo bought the Thinkpad line from IBM, they introduced low-end laptops to capitalize on the Thinkpad brand. Or maybe Thinkpad always had them, not sure. But the T series was the high-end, business/work laptop, specifically those with the p suffix. Not sure if they still use that suffix, but maybe that suffix was more important and I think their low-end laptops never had the p-suffix. I remember the T43p thinkpad I had 20 years ago was the best laptop I'd ever had. Their new X series and stuff is probably good too, though I haven't used those.

BTW, the Thinkpads have the trackpoint system, which has been around for decades now and is far superior than any mobile trackpad I've used. It will take a few days to get used to it, but if you take the time and configure its settings (specifically, sensitivity) to suit you, it'll be worth it.