Why is Really Simple SSL plugin necessary?

Is it normal to need to use this plugin every time I install an SSL certificate? I feel as though it is a fix for an issue that can be resolved when developing the site rather having the plugin do things on the fly as well as having to do a search and replace in my DB for mixed-content errors. I am not bashing the plugin in anyway, I’d have no SSL certificates without it. I just want to know if there is a way to avoid all of this by developing my sites with the SSL certificate installed beforehand (maybe)? Is that even possible?