Why is the <picture> element so rarely used?

Hey guys

I am studying web design and I was wondering why the <picture> element
isn't used so much.

There are a lot of tutorials about it:

http://www.html5rocks.com/en/tutorials/responsive/picture-element/
http://webdesign.tutsplus.com/tutorials/quick-tip-how-to-use-html5-picture-for-responsive-images--cms-21015

http://inspire.blufra.me/html5-element-and-bootstrap-4-media-queries/

And it's officially listed here:
http://www.w3schools.com/html/html_images.asp

However it doesn't seem to be implemented a lot.

Is it because I read that Safari only supports srcset in <img> but not
<source>?

So basically that + other small inconsistencies in browser support?

Or is it just that people are so used to <img> that they stick to that plus
stylesheet-based media queries?

Can anything be done to make this wonderful HTML5 element be used more?

Best

Liz