The same reasons people migrated to Python in the late 90s from matlab, Fortran and C++: Python addressed pain points in those languages and ecosystems. Julia addresses deficiencies in Python the language. Unfortunately, it lacks the ecosystem: until it gets the rich library set that Python has, we're stuck with Python since ecosystem is arguably more important for practical traction than the base language.
I don't know how well it works, but Julia does let you use python libraries.
@pyimport matplotlib.pyplot as plt
x = linspace(0,2*pi,1000); y = sin(3*x + 4*cos(2*x));
plt.plot(x, y, color="red", linewidth=2.0, linestyle="--")
plt.show()
There's been extensive discussion of that and yes, it may well happen [1]. The biggest concern at this point is how to avoid having people abuse such a feature by trying to fake out class-based o.o. code in Julia in a way that will look right but work poorly.
