As mentioned in a sibling comment, turbines don't scale down very well. Boundary layer friction gets relatively worse for smaller turbines, and AFAIU small turb

As mentioned in a sibling comment, turbines don't scale down very well. Boundary layer friction gets relatively worse for smaller turbines, and AFAIU small turbines have relatively larger inefficiency due to air leaking past between the blades and the casing, etc. There's a couple of companies working on recuperated turbine engines for small aircraft in the few hundred kW range, remains to be seen whether any of these will succeed.