sorry for grammar errors, i was in hurry.

City/county SWAT teams function within their jurisdiction.  Whether the perp does or doesn't have a hostage is irrelevant when he's violated state law and not federal law.  You wouldn't call FBI HRT (assuming they were even close by) because some cranker beat his wife and then barricaded himself in his house and refused to come out.  That's a local issue.

SWAT also operates in a permissive environment (for the most part).  

thanks mate. i thought similar. so counter terrorist teams have harder and more rigorous training than swat,right?

Federal agenies and  the military have a much more rigerous training and selection progarm than most SWAT teams.  There might be a few exeptions - full time teams like Los Angeles - but most part time SWAT teams couldn't hope to approach the proficiecy levels of FBI HRT, Delta, etc. 

It's just common sense.  Most SWAT members are patrol officers first and get to train for SWAT about eight hours a month.  Most teams have the best patrol officers in their departments - men who stay in shape, shoot on their own, and are motivated - no doughnut cops, etc. 

We have a rigerous PT test twice a year and make the most of our training time each month, but eight hours is only eight hours no matter what.  Thankfully the average nationwide SWAT sniper shooting a couple of years ago was estimated at 51 yards.  Basically, across the street.  The longest recorded was 187 yards.  We're not  Delta and don't claim to be.  Fortunately we usually don't have to be.

GOP,

The prognosis isn't quite as bleak as you think.  Everybody usually gets a 40 hour school each year in addition to the monthly trainings.  Also consider the average callout involves one suspect.

Joe Bob gets drunk and beats his wife.  Wife runs out of the house and calls 911 from the neighbors.  Joe Bob refuses to come out when the cops show up.  Joe Bob has guns.

The cops have patrol units and snipers on the outer perimeter.  Negotiations might go on for hours.  If the entry team makes an entry sometimes it will be more of a probe than a dynamic entry (situation dependent), flash bangs and gas happen, of course, but not always.  So drunk out of shape Joe Bob who doesn't shoot that often might be up against one or two stacks of 4-5 cops each, not counting patrol units and snipers on the perimeter. 

Seldom are shots fired.  Joe Bob goes to jail. 

I've never shot or been on a callout where shooting occured; just laid out there on the perimeter and watched Joe Bob walking past windows through my rifle scope.

Patrol units will be first on scene to a robbery of any kind.  SWAT will respond if it isn't over before they can stage and get deployed.  Depending on what's being robbed the locals could be relieved by the feds, again, if the negotiations go on and on and they can get there before it's over.