This happens so often that you would think the real bad guys would sometimes have the front door rigged with antipersonnel explosives. After a couple of SWAT teams got blown up, tactics would change.
Actually you have hit on the most fundamental f-up of these kinds of operations. If they DON'T know that an innocent couple is behind the door, then they also WOULD NOT KNOW if this is a terrorist safe house filled to the ceiling with explosives and heavily booby trapped. Unfortunately, I'm afraid that ballistic vests, some cowboy play on the firing range, and an overdose of self-important BS have left them convinced that they are invincible.
Not doing recon and knowing exactly what you are entering is just a symptom of piss-poor, armature, screw-ups playing with guns.
Which may explain why you never hear about SWAT teams going up against actual tangos.