Yes, being able to make a clear distinction is important, and subtle variations in pronunciation, whether officially recognized or not, do help. That's why, in

Yes, being able to make a clear distinction is important, and subtle variations in pronunciation, whether officially recognized or not, do help. That's why, in particular, people tend to say "fur" instead of "for" - in order (my guess) to avoid confusing it with "four" (which is expected to appear more often in everyday speech than "fur" and "fir").