Actually yes you CAN. The new Intel CPUs that are suitable for the MacBook Pros have only come out in the last month or two. And it will be the same long wait time for Kaby Lake mobile processors that are suitable.
Dell, Razer, HP, Asus, Lenovo, etc. have all produced laptops with Skylake chips similar to the MBP.
The 15" MBP is still using Haswell processors, never mind Broadwell, Skylake or Kaby Lake.
It's a great shame, as Apple used to be on the forefront of personal computing. It wasn't too long ago they had chips before any other manufacturer.
Quite frankly, I find it insulting that Apple still charge thousands of dollars for technology which is years old, without reducing the price at all, but there you go.