are you sure you're not confusing that with the app store? it's trivial to get the .apk from a bought app after it's on your phone, but it's not trivial to strip the playfair DRM off an .ipa.
I'd argue that while it might be easy today, that's just an implementation detail. The play store does not advertise anywhere that you can backup APKs for installation later in case an app is pulled from the store. Tomorrow Google could invent a new kind of delivery mechanism that makes this stop working.
Other countries may have different exceptions about personal use.
This site (HN) is hosted in the United States so you can post any link you want to here.
Please don't propagate the mistaken notion that a URL can be illegal.
Please, further, don't malign HN by suggesting that they would moderate a post discussing a digital tool.
You can discuss the LOIC here[1]. You can discuss DeCSS[2] here. You can discuss Demuffin[3] here. You can discuss ToneLOC[4] here.
[1] https://en.wikipedia.org/wiki/Low_Orbit_Ion_Cannon
[2] https://en.wikipedia.org/wiki/DeCSS