Cost of production. You can flow solder over an entire PCB in one go. And do many PCBs at the same time. Each crimp would have to be made individually, or with a machine which did several at once - and it doesn't take imagination to guess what that would cost.
Also, solder is reliable enough in this context for the design life - say about 5 years.
FWIW, the harnesses going to those PCBs will invariably have crimped plugs.