It's not suppose to, it's a minimal framework for a reason. If you really need a generator, as posted above, create your code in a laravel app and copy it over.
The idea that you need to install Laravel simply to use it's generators, then C&P over to your actual app is inane. I'm very curious why generators are removed from Lumen and wonder if they cause some sort of performance issue?
I agree, but I just type them out. So for me a non-issue. Possibly could make a package with generators and only require as dev environment. That way when your app is pushed no worries about overhead.