I will use Steam, because:
- SE will be paid (don't worry donaters, you will receive a free key)
- Steam has a lot of benefits for me:
-- built-in DRM
-- file distribution service (do you remember size of the Solar system addons?)
-- auto-update feature which ease uploading updates for me and downloading for you
-- as someone mention, Steam has 70% of the game market, so why should I ignore it?
-- centralized payment collection and transaction service
-- workshop for mods, including paid ones (yes, mod authors can earn money!)
----- to distribute from the web site, I need to implement all the above myself. It is months of work for a whole programming team!
-- Steam also has many small features, some of which will be implemented in SE later: achievement, cards, etc.
-- Steam has its own marketing/advertising system, which will help with sales.
- Those who have HTC Vive needs Steam anyway, because OpenVR (driver for Vive) is a part of the Steam.
One of the reasons why SE updated are so rare is difficult distribution. I have to compile and upload installer to many mirrors and torrents. Then if some critical bug appears, I need to repeat this with patch, then write instruction how to install the patch (and nobody reads it anyway). This is why I tried to make SE release as polished as possible, fixing virtually all critical bugs. With Steam, I can upload tiny fixes every day, and no one will even notice that. Implementing auto update directly in SE requires, aside from programming work, powerful file distribution system, which will cost money. Steam provides this "for free" (well, not for free of course, Steam will take some fee from sales). Also I need some DRM/cd-key protection system in SE, which Steam also provides. And, of course, I need whole web store to make sales. Paypal provides such functionality, but this requires huge web programming work (I am C++/graphics programmer, web programming is alien territory for me).
For those who have no internet connection: hey, we are in 2018! I planning to implement web data streaming at some point: SE will download Earth/Mars/etc textures from web storage on demand, like Google Earth. Instead of installing 50 GB of texture addons, you will need just internet connection and few gigs of disk space for the cache. Streaming will not be limited by textures, GAIA star catalog contains 1.7 billion stars, and estimated SE database size is about 80 GB. Also, in future SE will have some tiny server where it will store user discoveries and names/descriptions they have to planets. And this is SE planetarium, online SE game is also in plans.