One obvious answer: politics. There are plenty of countries where civilians are not allowed to own semi-automatic rifles. Too bad, then, that the most excellent website thefirearmblog.com is about “Firearms not politics.” BTW: Merkel RX.Helix. And hat tip to commentator Jesse.
Seems more like just a novelty than an attempt to get around semi-auto restrictions.
Straight-pull bolt actions go all the way back to the 19th century. Before they adopted a semi-auto in the 50's, Switzerland fielded the excellent K31 (wiki: http://en.wikipedia.org/wiki/K31).
Obvious disavdantages include a more complex (read: Expensive) mechanism, and not as easy to chamber a recalcitrant round (where a turnbolt gun can use the leverage of the bolt and the shooters strong right arm to chamber a slightly overlong round.)
Honestly a decent lever gun is at least as fast, as is a pump gun (very few centerfire pump action rifles, though) and faster even than this straight-pull bolt gun. an additional plus for the pump gun is that the shooter doesn't have to remove either of his hands from their position on the stock.
On youtube you have a film where ordinary hunters manage the Merkel RX-Helix. Classical use but very fast: http://www.youtube.com/watch?v=4LTFTohpErw