A search for voltage reference LM385B reveals that most of its many versions come in either 3-pin TO packages or 8-pin SOIC/TSSOP packages. Very few are 3-pin SOT-23 packages. I was wondering why is this? Why have 8 pin packages where 6 pins are NC?
There are multiple issues at play here, actually. Die size, as mentioned, is one of them -- a SO-8 or even a TSSOP-8 can accommodate a larger die than a SOT-23 can, although modern references are available in SOT-23 packages these days (the Intersil FGA parts come to mind, specifically).
Other reasons include mechanical stability for high-accuracy references and the need to provide post-packaging trim access due to packaging process induced shifts in the reference voltage. LTC AN82 discusses these problems in more detail.
Std Packages are selected for automation, so another tool adapter does not have to be purchased.
8-DIP, TO-92, SOIC and TSSOP are avail
The TO-92 has 3 leads like small signal transistors