Relay closes when pin is being pulled low?

Using Arduino Motors, Mechanics, Power and CNC
#1

I recently bought this cheap 4 channel relay board:
http://www.ebay.com/itm/171017956899?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

It behaves differently from the 1 channel relay board I already had:

My old relay board would close if supplied with 5V (HIGH) on it's pin.

This relay board closes when a pin is connected to ground (0V LOW).

Is there an explanation why some board close on HIGH and some on LOW?
In my mind it seems more logical to close the relay when supplied with 5V (HIGH) and not the other way around.

#2

The board you have linked has optoisolated inputs. I think it's more typical for these to be active low; I'm tempted to say they're "always" active low but then I'll probably get caught. :wink:

#3

Seems to me they should just invert the wiring on the LED and the opto and connect it to GND instead of VCC to make it an active high.

#4