When you need to upload images to your website the smaller they are the quicker your page will loadi. Saving the 10 seconds of download time might make the difference between somebody staying to see what you offer and lost traffic.
I use a free tool called: Optimizilla to compress my jpg & png images. It uses smart tools to give you the best compression and best quality for the smallest file size. AND you can compress 20 files at a time!