The reason one has to earn merit before he can send merit is prevent abuse.  Many newbies are likely abuse their sMerit by sharing it amongst their newbie buddies, thus undermining the point of having a merit system.  The premise is that if you've earned the merit, you're likely to know how to use it.

If you find a post worthy of merit, but don't have enough to send yourself, report it here:
https://bitcointalk.org/index.php?topic=5093271.0