Hogging out material
Yup - as Darren says - if they are sharp they are indeed a good way of removing material...maybe they are trying to save money on router cutters?
But personally - for me this would be an extra step...I'd rather just get on and route it. I have extraction on the router so it is relatively clean - hardly any escapes when 'pocket routing'
FYI: In 'The Factory' we used a larger router cutter for roughing and then a smaller one just for going round the edges. Sometimes I replicate this with my hand held routers - i.e. have a (large general purpose) roughing out cutter and a (smaller and newer) 'final pass' cutter.
Measure twice, cut once...