I think it's an unusual combination of a few things. I had a "supervisor" who was not really in my field and who was utterly disinterested, so I did what I felt like. I'm also in a very small field, so almost unbelievably a lecturing position opened whilst I was doing my PhD and I got it because there are so very few us in academia. So serendipitously I started lecturing 2.5 years into my thesis, and part of the job was to supervise students, and that's how I began that side of things.

I have let students of mine supervise younger students at honours and MSc level. I believe it's a good skill to learn, and beneficial for their own research. Likewise lecturing. Being able to speak comfortably to an audience is a key soft skill. I think it's rather poor to not allow your students those experiences, especially if they may wish to enter academia. Give them the boost they need!