why it is not a free app?
I'm glad they did it. 3 dollars is nothing compared with the value I got from being able to use python on my phone.
The real question is: why the sense of entitlement?
... on a platform that is definitely not free/open, and definitely not on the low end of the price scale.
"Free" software is great, except for the expectations some bring that everything should be free, and nobody should profit from their efforts - except for Apple apparently.
I use a mix of Apple products and F/OSS software, and I am happy to pay for quality products when they satisfy a need, especially from small or independent developers.