Why doesn’t my custom font copy-paste correctly into Google search bar or other apps?

I created a custom font using FontForge/FontStruct. The symbols display correctly when I type in Word or other editors that use my font.

But when I try to copy and paste the text (for example, into the Google search bar, a chat box, or other applications), it does not keep my custom symbols. Instead, it pastes the fallback characters like A/B/C from the default font.

My goal: I want to copy and paste my new symbols anywhere without assigning Unicode values to them.

Is this possible? Or is Unicode assignment always required for copy-pasting custom symbols across different applications?