One reason that someone might want to do this (besides learning about ec2) is if they are itinerant. For example, suppose you work for a company where you travel a lot and there are restrictions on vpn usage--you could start an instance of this (assuming that you can still comply with the IP/PII policies of your workplace) and access it from anywhere.
Another thought--if you are playing with web services such as twilio for example, you need an IP address for the response to your REST requests--this could be a problem for people doing development at home without a static ip (sure, you could use localtunnel, but this does have some appeal). This way, you can test this on your development machine without going live...
This is exactly why I set up my first (and now my second0 EC2 instance for development. I've been playing with services that need an external static IP address. My ISP is pretty hostile towards that kind of thing, and it's a PITA if you're travelling and need to do some work.
Another thought--if you are playing with web services such as twilio for example, you need an IP address for the response to your REST requests--this could be a problem for people doing development at home without a static ip (sure, you could use localtunnel, but this does have some appeal). This way, you can test this on your development machine without going live...
Anywho, just a few thoughts.