My pet theory is that a lack of non-whitespace separators heavily discourages clever one-liners or compact sequences of operations and forces the programmer to write more readable code.
python3 -c 'import math; tau=math.pi*2; r=1; u=r*tau; s=r*r*tau/2; v=r*r*r*tau*2/3; print(u,s,v)'before_loop; while something: step1; step2; after_loop;
Note that after_loop is still inside the loop. Also you can't have multiple colons on the same line, so this doesn't work either:
if test: do_this; else: do_that
That gives a syntax error