You don\'t have to, but we recommend it for performance, SEO and functionality issues.
If you are looking for a SVG editor and don’t have tons of money for Adobe Indesign, check out Inkscape (free) or CorelDraw (cheap).
All further information and background story: http://www.jenskuerschner.de/svg-images-with-png-fallback-in-wordpress/
This usually happens if your server does not allow fopen or if the svg file does not contain any size information. You can workaround this issue by adding height and width information to the shortcode?
Is there a svg file with the exact same name (except the file extension) in the exact same folder? Did you input the tag manually and used single quotation marks? If yes, change it to double. Does you server allow fopen? If not, the auto-change will not work, because the engine cannot check if the svg file exists. Did you specify any size information (width; height)? If not, do so! Most SVG files do not contain those information.