Well, it depends on what you are after.
I like pipe organ, and the grand organs can play as low as 16 Hz. So a Sub is necessary to reproduce the full range of an instrument like that. Likewise, for HT, the LFE channel contains information from as low as 1Hz up to 120Hz.
On the other end, you may not hear above 20000Hz or lower depending on age or damage to your ears, but some will say that content above can add detail, clarity, or “airiness.” Some tweeters can play accurately beyond human hearing on their own, others not so much.
In some cases the inclusion of this data is marketing fluff, and in others is necessary info.