I wouldn't say that the concept of romance is completely missing from the Miqo'te, however. Given how few men there are, it's quite likely that romance does occur - mostly between members of the same sex. Nothing really suggests that the Miqo'te have a lowered drive or need for companionship (which is evident in that there are Miqo'te outside of their tribes who DO desire such things). They approach the act of propagation far differently than most races, but I'd wager that romance is not an alien concept even within the tribal structure, just a more open concept.