Because there are a lot of issues with i9s in those form factors that leads to less perf than even an i7 from the same generation.

There was a Linus Tech Tips the other day about how even current gen Intel laptops can see better perf on an i7 than an i9. It looks like the i9s simply don't make sense in this thermal form factor and are essentially just overpriced chips for people who want to pay the most to have the biggest number.