It’s pretty fundamental social psychology, really. People care about the number because it’s loosely connected to status within the group, and it’s quite normal for people to be concerned with status. It’s also quite normal for people to claim not to be concerned with status.
In this group, you acquire status through a combination of several factors: length of active participation, the value of your input, and volume of participation. Since all of these will nudge your lurve score upward to some degree, there will be a very rough correlation between your status within the group and your score. Plus, we reinforce that perceived correlation through the whole party and award scheme. Once that correlation is overtly established, it’s inevitable that the number itself becomes an object of concern.
Then you have the curious little dynamic whereby it’s considered ignoble to be concerned with status. No matter how much status actually means to you, evidencing that in any way will lower your status. In fact, you can actually elevate your status by proclaiming that status (and, by implication, its markers) means nothing to you. That projects a strong security in your sense of status, so that you don’t even feel that it’s worth monitoring. To someone lower in the ranks, that show of insouciance signals someone of unshakeable status.
How much you truly care about lurve scores will depend on several things. One is whether or not your needs for social status are being adequately satisfied outside of this group; if you’re respected and looked up to in other social contexts, then it might not matter so much here. Another is a matter of personality; some people are natural “social climbers” or have highly competitive natures. Others see that they have little chance of climbing the status ladder, whether through lack of time or just not fitting into the culture, so they lower their expectations of getting status here and seek it elsewhere instead. For them, Fluther is likely to serve a more utilitarian than a social function.