I sometimes see the wires of winding are twisted outside of the transformer (or inductor), as seen in the images below. What is the purpose of this? When should I twist winding wires and when shouldn't I?

(Note: This is not about using multiple twisted wires as a single wire inside a winding (i.e.; Litz Wire).)

I sometimes see the wires of winding are twisted outside of the transformer (or inductor), as seen in the images below. What is the purpose of this? When should I twist winding wires and when shouldn't I?

As two conductors come closer and closer to each other, the capacitance between them increases. Wouldn't this parasitic capacitance between the wires cause problems at high frequency ferrite core inductors and transformers? Driving them will be the same as driving an LC tank circuit. There will be overshoots and ringing fluctuations. What trade-off does make us accept these side effects?

(Note: This is not about using multiple twisted wires as a single wire inside a winding (i.e.; Litz Wire).)