Dragging an app to Applications does feel quite an anachronism when you come from the land of the iPhone and iPad (and Windows), when you open your first MacBook Pro or Neo.
It's one of those things that isn't entirely obvious or intuitive. Especially when the helpful arrows and instructions are customised and up to the app developer to provide, and have gradually faded and vanished over time. Someone probably has to show you what to do when you see the DMG window for the first time.
This probably needs to change. Apple tried to fix app distribution with the Mac App Store, but of course, DMGs and ZIP bundles still exist. As they should.
While DMGs are loved by Mac traditionalists for their almost magic simplicity, you could argue that the PKG, while more involved, is actually a great deal more straightforward with its InstallShield-like wizard.
So yes, allow people to drag apps, so they can drag them wherever they want. But since pretty much everyone is going to drag apps to Applications anyway, we should provide a button in the disk image saying "Install" or "Add to Applications". Of course, "install" is a slightly odd term in Macland, but it's a well established term in iOS. And on macOS, it's even inconsistent within the same platform, with "install" buttons in the Mac App Store.
I also think it's high time that we fixed app uninstallation on the Mac while we're at it. We have the widely shared and celebrated lore that uninstalling an app is as simple as dragging it to the Bin. Another example of Apple magic. But this is frankly a tall tale we tell ourselves and propagate to others. You will often be left with hangovers of the deleted app scattered all around the filesystem. Orphaned configs, user data and binaries galore remain in ~/Library/Application Support, Library/Application Support, Library/Preferences, Library/Containers, dotfiles in your home directory, and so on and so forth.
We end up in the bizarre and fragmented situation of Bin-dragging, uninstallers and third-party Mac cleanup utilities. For example, the Windows-style uninstaller programs bundled with Adobe apps, because things like Photoshop were created way back in the 90s, and they have a legacy of lots of helpers, utilities and configs in a multitude of places.
In the era of sandboxing, containers and fine-grained permissions in macOS, we should be able to track apps better, and have deeper OS support for installs and uninstalls.