Though jammers ARE extractable, I've never actually seen anybody do it... Seems like the rounds are short enough, and jammers are in grand enough supply, that people don't even consider extracting the "disposables."
Whenever I place jammers, they're in excellent locations - and I wouldn't want to lose them in any case.
Back on point, however, driving an EMV truck into the base is faster, safer, and you can help defend the cutter as it does it's minute long capture routine. When you're done - it's one extraction, instead of seven or eight. Less resources deployed, less chance at the enemy gaining a point advantage on you!