You can thank the bounty system for that. Besides the strikes bring nothing new in form of content and the worlds most expensive game just wants you to shoot at a bullet sponge for an hour. So far I have not reaped any rewards for taking my time in each strike. Though I very much understand your point, I just don't think most gamers would agree with you in the form of Destiny's tone of rewards. Taking your time does not really matter. I swear it feels like I've done each strike about hundred times before, all with no plot, bad loot (though thats finally being fixed slowly) and no world saving purpose. Perhaps the only minimal redemption of running through a strike may lay in the form of a legendary/exotic item granted at the very end.