If you were to approach a non-tech person and ask them how many open source apps they use on a daily basis, they would probably say "none", even if it's not the case.
But even so, that doesn't seem informative. Ask any user how many "Qualcomm apps" they use, or "Meta apps", or "Intel apps". No one knows where this stuff comes from. They buy a phone with a label on the box and then download stuff from an app store.
That's not a statement about how the software is produced, it's just how the market presents products to consumers. People don't know where the gas that goes into their cars comes from either, but that's not an argument that petroleum distillation technology is a failure.
Can you explain what you mean by this? As far as I am aware, an application (aka "app") is a piece of software.
You literally exercised huge amounts (seriously: millions of lines!) of open source code just now, in the process of posting that very comment and transmitting it to me to read.