Purpose of the Latch Enable (\$\overline{LE}\$) and Ripple Blanking (\$\overline{BI}\$) pins on 74HC4511
If the 4-bit data input to one 4511 is being shared with another 4511, LE allows you to set-up the 4-bit data for one device (then store it on internal registers). Then you can set up the appropriate 4-bit data (using the same data lines) for another 4511 and have a separate LE pin to store this different data to the 2nd device.

If you didn't have this feature you would have to use 4 lines dedicated to each driver and that is inefficient.

The blanking input disables all segments.