If there is no literal rebirth, why have samvega (a sense of urgency)
Why have samvega (sense of urgency that death may strike) without believe in literal rebirth?

You could argue it both ways. Why have sense of urgency if you will be reborn? On the other hand - Why have sense of urgency if you're not going anywhere?

Dharma is called "Safe Bet". Whether there is literal rebirth or not, Liberation is deathless. Whether there is literal rebirth or not, dying without Liberation is scary - because either you may go to some strange inhuman worlds, or you disappear forever.

Hence the sense of urgency to attain Liberation.