I completely agree with Cookiemonster,
Also, by knowing Brix levels, you can deduce that a fruit was not optimal either due to rain, improper fertilization or perhaps the tree was too young. By knowing the optimal Brix levels for any given variety, you can adjust your fertilization or harvesting schedule accordingly.
Commercial groves use Brix readings to determine when Fruit should be picked.
It is true that Brix readings can be misinterpreted. A high Brix reading does not necessarily mean a piece of fruit will taste good because taste also depends on acidity, how it smells and for many people how it looks. Having said this, for any given variety, let’s take Lemon Zest for instance, a LZ with a Brix reading of 25% would in most instances be peferred over a LZ with an 18% Brix reading.
I believe some people are also not properly using their refractometer by forgetting to calibrate it or by squeezing juice that has too much pulp in it which will give a false high reading.
Simon