I'm doing some experiments with an LCD 1602 and have come across this issue.
Arduino libraries (or at least some) allow the user to ignore the R/W pin of the LCD 1602 and simply connect this to ground (which forces the device into a write-only mode). That would appear fair enough because usually you want only to write to a display, not read it. However, the data sheet for the HD44780 chip set, as used by the LCD 1602, has this note:
Note: Be sure the HD44780U is not in the busy state (BF = 0) before sending an instruction from the
MPU to the HD44780U. If an instruction is sent without checking the busy flag, the time between
the first instruction and next instruction will take much longer than the instruction time itself.
However, in order to test the busy flag, the device has to be in read mode. I guess that then that the decision has been taken to accept this time penalty ?
HD44780 Data sheet: https://www.sparkfun.com/datasheets/LCD/HD44780.pdf
Sample LCD library: GitHub - arduino-libraries/LiquidCrystal: Liquid Crystal Library for Arduino