Players don't know jammers?

I just got out of a mission lvl7 bots and the host and his group died while I was assaulting a jammer. After spamming the reinforce button I told them that I couldn't reinforce until after I'd turned the jammer off. When I did turn it off I immediately called them back in and the host proceeded to kill me and take my stuff. When I got called back in I did the exact same thing back and reclaimed my equipment. Dude kicked me but oh well, they were struggling on their own so while I completed the mission by myself I doubt they had any success. But seriously tho. How are people playing on level 7 bots and still have no clue what a jammer is/does? Does anyone know why these people are like this? (Aside from standard griefers, this dude wasn't a griefer just an idiot)