Once I "install" an application, for example libreoffice:
- It works even if I do not have a working Internet connection (or back in the day, even if I had removed the original media from the drive);
- It works even if the original is gone.
That is, by "installing" an application, I gain a permanent, offline, working copy of it.
On the other hand, PWAs (Progressive Web Apps) also work in offline mode without a "traditional" installation step.
Please stop saying this as if it is in any way acceptable. Some parts of the computing world work like this, but this is not, nor should it ever be, the new normal.
You can still definitely use your computer without resorting to such licensed crapware.
"Traditional" applications that are subscription-only are only partially installed, if their full functionality requires always-on connectivity.
Stay offline for 30 days (iirc) and try to play the games you paid for.
The maximum speed of moving data from one physical place to another, moving data from the hard drive to the motherboard and the ram to the cpu/cache is faster than from the internet to a computer. To he speed of light is still noticably slow when you're making round trips to get data.
The other issue is configuration, even if automated, software needs to make decisions about how to deal with different hardware and system differences. This takes time to bootstrap after initial load increase time to usuability or it can be done on the fly slowing down the interactions.
Of course this goes hand in hand with an instant start (no dreaded splash screens please), and not having to download gigabytes upon gigabytes of data upfront.
Modern web apps might be bad at this, and browser engines might be bloated, but native apps aren't any better (even heavy web pages still load many times faster than - for instance - starting Visual Studio or Photoshop).