It matters if you regularly dump huge amounts of text to the terminal. In other words it rarely matters to most people. In fact, if it did, more people would realise that the terminals they use are often quite slow compared to ones like e.g rxvt.

Most terminals don't even implement most well understood "hacks" to keep up with the apps they're running (e.g. "render" to a text buffer and render the text buffer to the screen separately and decoupled (multiplex or on separate threads)), because people rarely are affected enough to care.