If you’re a modern developer, then you use JPG files. Doesn’t matter if you’re a web dev, mobile dev, or some weird sysadmin who just sends around memes all day. JPGs are a part of your job, and critical to the experience of the users who benefit from that work.
https://medium.com/@duhroach/reducing-jpg-file-size-e5b27df3257c#.lr52h5hdb