It's best to see once than to hear (or read) a convoluted explanation a thousand times.
I just wanted to answer one question and it was begging for a drawing. So I thought, OK, I draw it on paper, then photo, then send to myself , then edit, then upload. And at that point I decided it's not worth it.
When we speak physics we speak formulas and drawings, so in this particular SE a drawing applet should be bolted to the editor and this is the feature I hereby request :D.
Feature requests of this magnitude are usually very hard to get past the Stack Exchange team.
On one hand, this sort of script is very heavy and it significantly adds to the page load times, particularly for users on slow connections. We already have one relatively heavy dependency (MathJax), and adding another one would slow the page down significantly.
This means that for the team to give this the green light there needs to be a very strong case that it is really necessary - on the same scale as MathJax, say. (Or, say, on the same scale as the circuit editor is necessary on Electrical Engineering and the YouTube embedded player is necessary on Music and Movies & TV.) For relevant past requests on this site, see here or here.
Building this sort of thing is also a huge amount of work for the developers, and in fact most such feature requests are only implemented if there already is a working implementation. This means that if you can sit down and code the feature you want, there's some chances it will be implemented, but if you want the SE dev team to write an awesome drawing app for you, you'll be waiting a long time.
This applies even from the tiniest of feature requests (many of which are already implemented in SOUP but are yet to be pulled into the main site, and it applies to feature requests with huge popular support like arXiv trackbacks.
That said, if you do find or write a suitable app, it is perfectly possible for individual users to mount this on top of the site via a user script. For examples, see StackApps.
So: if you really feel strongly about this, then start coding.
While you're waiting, I use Google Draw to create diagrams for my posts on the Physics SE. It's free, and with some practice you can create reasonably convincing diagrams. You can download your drawings in a variety of formats, though I usually just screen grab and paste into my favourite bitmap editor for tweaking.
