It would take me some effort to make and maintain a separate version. Users would report bugs which have been fixed months ago, because they did not update it, etc.

I think the importance of "offline apps" is overrated today. Personally, I spend less than 10 hours a year on a device without internet, and I think this number is decreasing each year, for everyone.

People use Google Maps and Wikipedia without having them on their hard drives. On the other hand, it is nice, that you can simply close a website and there is no track of that service in your computer.