I’m not sure where that comes from, but I have to fight it constantly. My key piece of advice on wiki page design, for instance, is that the first question the person has is “am I even in the right place?”. The first or second sentence has to tell someone why they should care about (or not!) the rest of the page.
And I find myself violating that advice at least once a week. It’s hard but then most important things are.
all I did was open the splash page and then close it
I would expect over 50% of users to take that first step. That is what I saw in similar scenarios.
That's why splash pages (and writeups, like the original) are important. But as mentioned in my previous comment, those splash pages/writeups also have to be effective advertisements.
without any explanation of why I should use your app,
or even how I'm supposed to use your app, I would
close it immediately.
It wasn't until many months later, after experience with other sites with similar interfaces, that I actually started using HN because I then understood how and why to use it. The HN interface is intuitive enough and similar enough to other website to understand that you're being shown comments and a reply box when you click on a link.
That's not the case with this [1]. If you linked me directly to a page that looked like this, without any explanation of what these boxes of text are telling me, where they are coming from, or what they are, I would not use it. The button next to them (a grey box with a plus symbol on it) doesn't explain to me at all what it does, and is not something you see enough in other apps to make a good enough guess as to what it does. After reading the blog post, my assumption is that clicking that button is supposed to send me an email, I think? But I would have absolutely no way of knowing that if you just linked me directly to the app.
1: https://hackernewslater.com/images/hacker_news_later_screen_...
edit: if you download the actual app, the first page it shows you actually is a splash screen that gives a brief explanation of what the app does and why. If that same splash screen content had just been shown and linked to at the top of the original writeup, I suspect he would've gotten a lot more installs.
The button next to them (a grey box with a plus symbol
on it) doesn't explain to me at all what it does
If the intention of the writeup was to discuss the process behind building the app, it apparently was successful in getting attention and generating discussion. If the intention was to get app installs, then this is a case that really could've benefited from a TLDR at the top, or at least a more direct, more obvious link to the app.
And I'm not convinced that it being a web app would have solved the issue, either. A writeup like this that linked to the webapp would face the same issues as described above. A direct link to the webapp would probably have me open it, spend 3-5 seconds looking at the splash page, and unless that splash page gives me a TLDR hook and a reason to actually stick around, I'd probably close it. In that case, your user engagement metric might include that as me having "tried" the app, but in reality all I did was open the splash page and then close it.