Is a buffer solution really inactive beyond a range of pKa±1?
The 10:1 ratio is really just something convenient for the chemists.  The buffer still works outside this range.  True, its effectiveness against base addition decreases with the amount of available acid at high pH, and vice versa for acid addition at low pH.  But if enough capacity remains, you can still live with the buffer even outside the 10:1 range.

Er, actually you do.  Our main blood buffer, based on dissolved carbon dioxide as the acid and bicarbonate as the base, has about 20 times as much bicarbonate as carbon dioxide (https://en.m.wikipedia.org/wiki/Bicarbonate_buffer_system).  Factors other than what a laboratory chemist calls "optimal" should be given their due.  Metabolic processes commonly produce (weak) acids, and the solubility of carbon dioxide is more limited than that of bicarbonate salts.  Both of these factors make a base-rich buffer desirable.