In an ancient textbook I was reading, they were explaining how to debounce with transistors, capacitors and resistors - so at one time in history debounce was done in hardware.

In my own brief stint in (non-critical) hardware development, all debouncing was done manually in software.

It all depends on application.... and perspective...

Hardware debouncing works well for most applications but may not be financially rewarding at scale. With time and effort software debouncing can render sometimes better/good or good enough results as hardware..

Remember the saying, "When all you have is a hammer, everything starts to look like a nail..."