Example is Cryptassist, the orignal plan was to end the ico last August, yes it stopped but resumed this month (will end Sept 30). The initial plan was to stop bec. of market condition (most probably) and was decided by equity investors which some got disappointed but later most agreed that it is for the sake of project and its investors.
Yes, that's what's on my mind as well. It has something to do with the market conditions and they have to adjust with it.
If an ICO didn't managed to reach their targets from the given time of 2-3 months, they would extend more. I rarely see those ICOs that are extending since I'm not really interested with nor investing to them. But some that can't reach even the soft cap even after that long period, they are stopping the ICO as they see no interest with it.