Survivors who stop doing gens

I am still shocked, after more than 1000 hours in this game, how often all three of my red and purple rank teammates stop doing gens and just wait for the last one to pop. Sometimes my teammates stop doing gens when there are three left.
Just played against a really bad doctor. All four teammates alive with one gen to go. All three did nothing while I was chased, and I kept him busy enough for three gens to pop. It is just so truly shocking to me how often survivors just stop playing. How can they not know how common that is? And how often it leads to killers getting easy wins because it's kinda hard to go 1v1 with four gens done? I'm always the only person doing a gen, injured, why my three teammates are fully healed and standing behind a stack of tires just waiting. Solo queue is so painful most of the time.