Hmmmmmm mayhaps make them playable on browser for people with worse computers, or people who have so many other games that they can't download it UPDATE: the language mods are now built in
You mean the mods, right? Well, having full mod support on the web version is going to be difficult. Browsers just make it hard to do mods. Currently, even a simple thing like a language mod has to be hosted on a server somewhere so that the web version can install and use it. As for storage space concerns, the game still needs to download and install it somewhere, so it’s using your storage space. Mods are a few kilobytes at the moment.