One of the most known reasons is the quality of images tend to differ quite significantly. PNGs tend to be higher-quality, thus looking more appealing on the website. This is a big reason why you would want to consider PNG format over JPEG. However, you will have to take into consideration the size of the file, as you don’t want your website loading times to be crazy.
Adding to the point above, PNG format is lossless thus meaning it’s great for graphics. In reality, JPEG format is better for photos and such, however, if you want a bit of animated text or a cartoon on your website, PNG will most likely be the way to go.
You can read more about the difference between PNG and JPEG here.
“The JPEG standard (ISO/IEC 10918) was created in 1992 (latest version, 1994) as the result of a process that started in 1986. Though, this standard is generally considered as a single specification, in reality it is composed of four separate parts and an amalgam of coding modes.”