I guess it might be my lack of experience, but why are rewrites bad ? It's a prototype because when you start a project : - you don't understand what the clie

I guess it might be my lack of experience, but why are rewrites bad ? It's a prototype because when you start a project : - you don't understand what the client wants - the client themselves don't really understand what they need (and sometimes, not even what they want, which is magnified as soon as you have to deal with multiple people) - you might not know how to achieve that - you might have an idea how to achieve that, but not have practical experience in it - reality (including funding limitations) restricts what solutions can be implemented - the usual code entropy... Given all of the above, why would you NOT do a bottom up rewrite at least once ?! P.S.: And in the cases the performance critical bits can be isolated, Python can outsource those to performant languages like FORTRAN or C. I am guessing the answer usually is : the funding doesn't come directly from the end user, and so the incentives are not aligned for a successful project - which also explains why software projects have such poor success rates (~10%) ?