Because the writer is accustomed to Python as their language of choice? Maybe it's a Python shop? What if they want to integrate it into their Django site?
If you're coming from a primarily Python background you won't just be waltzing right in and using CPAN modules right away. You have to understand the underlying language as well. Python and perl's object oriented systems for example are quite different (using Moose helps somewhat granted the person knows it even exists). Then there's the issue of understanding various contexts. These differences may take time getting used to depending on the level of the developer.
Python also supports regex as well, which can be useful for weird situations. Granted however it's not going to be as tightly integrated as perl. There's even a Natural Language Toolkit if you want to get really crazy with things.
TLDR: Right tool for the job should take environmental circumstances into account as well
If you're coming from a primarily Python background you won't just be waltzing right in and using CPAN modules right away. You have to understand the underlying language as well. Python and perl's object oriented systems for example are quite different (using Moose helps somewhat granted the person knows it even exists). Then there's the issue of understanding various contexts. These differences may take time getting used to depending on the level of the developer.
Python also supports regex as well, which can be useful for weird situations. Granted however it's not going to be as tightly integrated as perl. There's even a Natural Language Toolkit if you want to get really crazy with things.
TLDR: Right tool for the job should take environmental circumstances into account as well