Beacause it would make writing fast code inconvinient, it's a tradeoff, a right choice clearly imo. How often do you need BigInts?
I try to use Julia instead of Python now if I don't need specific libs, it definitey feels like a nicer language to me (i.e. I can get stuff done faster).
In any case. If you think of it as a nicer C, it works very well. It is a slight disappointment if you think of it as a nicer Python.