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[on:]

For instance, that kind of switch one encounters often : https://www.sparkfun.com/products/97

Edited: inappropriate e-mail link replaced by an url link.

[Reply #1 on:]

For instance, that kind of switch one encounters often : https://www.sparkfun.com/products/97

To make it harder to figure out how to wire it up of course.  

 Actually the most likely reason is mostly for more mechanical strength as the switch is going to be pressed a lot and two connections would not be nearly as stable as four.

Lefty

[Reply #2 on:]

Also the legs act as an anchor while the circuit is being wave soldered.

[Reply #3 on:]

Why is that link a "mailto:" link?!

The reason is a combination of:

2 pins is mechanically weak, 4 pins means more options for routing traces past / through the PCB
real-estate under the switch, some switches with the same footprint will be SPDT and need at
least 3 pins anyway.   There is a cultural bias in favour of rectangles over triangles/hexagons in
engineering too (for instance the standard QWERTY keyboard can be more logically made from
hexagonal keys rather than square, yet hexagonal key switches are never seen)

[Reply #4 on:]

Why is that link a "mailto:" link?!

Because the mailto: link button is right next to the hyperlink button.

The pic attached is a good reminder of how those pesky little switches need to get wired.

[Reply #5 on:]

Yet another reason to have two pins per terminal is that the switch can then double as two jumpers.  This can allow a single-sided PC board design and thus save money over a two-sided design.  Traces traveling one way can use the switches to jump over traces running perpendicular to that direction.

[Reply #6 on:]

Thanks everyone !