I don't think anyone quite appreciates the level of effort required to publish a game on Steam. Or anywhere else, for that matter.
I've begun preparing the Store listing for Super Multitasking GO!, the upcoming free-to-play version of Super Multitasking. Of course you need to prepare system requirements, write a description, and post some screenshots; that much is obvious. But the amount of additional artwork you need to prepare is downright mind-boggling. You need to prepare boxart for the Steam gallery view, artwork for the Library page, and a number of images for the store listing, all in different dimensions, of course. You need to prepare artwork for every single Achievement you've added to the game: a "locked" image as well as an "unlocked" image. And if you want to offer DLC for your game, most of that also needs to be done for every single piece of DLC you're offering.
Of course, you'll also need to implement and test those Achievements, as well as stats and Leaderboards. You need to test the game with every kind of controller that you officially support. You should probably implement Steam Cloud for saved data, and you'll need to test that also. And you haven't even uploaded the actual game to Steam yet...
Presumably, larger developers and/or publishers have folks on staff who handle all of this while the devs can focus on the game itself. But when you're a one-man show, you have to handle all of it yourself. Now, if you're wondering why games from small devs either take forever to come to other platforms--and when they do, it appears as if they contracted a different developer to handle the port--it's because the effort to release on another platform is also enormous. Here's an example...
I toyed with the idea of releasing Sharpshooter Plus on Android. A winning idea, right? The game is SO much fun on touchscreen! I got it running on an Android tablet in a day or two. Easy peasy. But releasing on Google Play is a nightmare and a half. First off, there's the process I mentioned earlier: description, screenshots, artwork. The artwork Google is looking for is (of course) completely different from what Steam requires (which is also completely different from what Xbox requires, etc). So it's kind of like you're starting from scratch. Platform features like Leaderboards, etc. are also implemented entirely differently. And then some platforms have unique requirements on top of that.
Google Play requires some crazy digital signing process that I've wasted many hours trying to complete, to no avail. Also, they require that you publish a physical address in order to charge money for anything. They claim that this is to satisfy legal requirements, but literally NO other digital platform requires this, so I'm perplexed as to what legal requirements Google is referring to. As I don't wish to publish my home address on Google Play, Sharpshooter Plus for Android unfortunately will never see the light of day. If you would have enjoyed it, I'm sorry about that.