Because you should.
Syrian security forces have killed at least eight people in a raid on the town of Kanaker near the capital, Damascus, rights groups say.The protests in Syria are a big deal. Syria's regime, under President Bashar al-Assad, is...well, let's just say that they're not exactly a stabilizing force in the region and leave it at that. Their link with groups such as Hezbollah is widely speculated, and numerous border issues and disputes with Israel remain. Internally, Syrian politics are somewhat Byzantine, and even though things might be "better" under al-Assad than previous generations, political dissidents and opponents are still routinely harassed and imprisoned by agents of the state. No "free-speech zones" here; just no free speech period.
That's what is happening now, of course. Like many groups in the region, the people of Syria have pretty much had enough of both the political and economic status quo. Like Libya and Iran, and unlike Egypt and Tunisia, Syria has used significant force against the protestors, who have numerous demands including democratization, legal reform, media freedom, and the end of al-Assad's reign. Like in for example Yemen, al-Assad has promised minor reforms, but nothing serious.
In the meantime, such as in the case of the raid at Kanaker mentioned above, the state continues to use serious force against the protestors. The opponents of the regime in turn seem to show no signs of giving up anytime soon. This is with good reason, since as many as 1,400 protestors may have been killed since the protests began in March. There is a feeling that too much has already been given up, and that the regime's ability to continue its oppression is breaking down.
The difficulties here for the United States are numerous. One, no matter what the result of the protests, there could be very significant effects on Syria's relations with Turkey and Israel, both U.S. allies. A victorious al-Assad may be emboldened; a newly democratic Syria could go either way. No one can really be sure. Secondly, the United States has much less leverage on Syria than it did with, for example, Yemen or Egypt. Bashar al-Assad has not been our greatest friend, nor we his, owing mostly to issues surrounding Syria's relationship with Israel.
There are also fears - amongst allies such as Turkey specifically - that the fall of al-Assad's regime could result in Syria fracturing amongst factional and sectarian lines. This of course would destabilize things significantly, placing an additional security burden on Israel and Turkey specifically. Things are already unstable enough in the region without an additional powder keg, after all. I mean, what could possibly go wrong if Syria fell apart? Surely nothing bad could come of that...
To date, the United States has shown some vague, tacit support for the goals of the protestors, but could and should do more. Intervention is a non-starter, of course, but the United States needs to seriously establish credibility with the leaders and general population of the anti-Assad movement. If the protests gain more traction, we should attempt to induce Assad to leave peacefully. If and when he is gone, we should then offer our full support to help Syria develop a new system and government for itself. Doing this is vital to ensuring that a post-Assad Syria does not fall apart. And given what it would mean if it did fall apart, this should be one of our primary priorities now.