Then the language itself offers trivial iteration, possibly in real time with tools like jupyter, and requires substantially less bootstrapping knowledge than something like C/C++, which creates a low barrier of entry for non-programmers, who are less likely to shoot themselves in their feet with memory management and such. And if you're concerned about performance, most of the standard data science packages are just wrapped C/C++ anyway.
Sure, it's not perfect, but it's practically the lingua franca of data science right now, and it fits the role quite well.