A lot of those units operates as a team of six or seven whereas your regular patrolman is lucky to have one partner and maybe a backup that's a few minutes away. This constitutes an army in most urban settings and the mere force of them directed at one place is enough to make things happen a lot quicker. You throw in the fact that most drug warrants are served at 4-6 am in the morning when most druggies are passed out or at their worst part of the day it makes for an effective force. It's a misnomer that those officers have more reasonable policies that "tie the hands of regular officers" In fact a good TAC squad have more rules they have to follow, the reason being is that these people go in keyed up and with heavier weapons if they screw up, they or their teamates will most likely get their head blown off. Plus they are civil servants they have to play by the rules like every one else on the force otherwise they are just an assasination squad. The validity of no-knock warrants is still being debated, yes they are effective, but recent studies have shown that executing a raid in surprise is actually more dangerous than traditional knock warrants with the same individuals and Special Units. That being said I firmly believe you can prove anything with statistics if you play with the numbers a little. So take from it what you will, I doubt that "SWAT" teams will go away, I just think that most departments have them just to have them, and there are relatively few cities that actually need them.