Scrabble is an odd game, because it's not really a gamer's game. While there is some strategic game play involved, its fairly straightforward and obvious. On the other hand, it definitely requires a good vocabulary -- or at least a good vocabulary of certain kinds of words.
On the other hand, there are many Scrabble players who don't play any other game. It ranks among those few games (such as Chess, Go, Backgammon, Diplomacy) that have their own devoted following with clubs, tournaments, magazines, etc. Like those other games, being a top-flight Scrabble player requires the kind of single-minded study and devotion that the casual gamer is not going to muster.
That said, it is a fun game among casual players and a great way to pass some time so long as everyone is more or less on the same level.