What is the centre hole for in modern train tracks? LEGO train tracks have 3 holes in each of the segments:



I understand the two outer holes are used with a throw-away piece to keep  them stacked while shipping, but what is the center hole for? Is it just for saving a bit of plastic? Or perhaps just a planned 'shipping' feature that was never used?
The larger hole is present in older 9V track as well:



I've never actually done this, but I've always assumed that the hole is there so that the track can be screwed or nailed down if desired to create a semi-permanent layout. This is common practice with traditional model railroad track: