On the other hand, stealing session tokens is typically going to require reaching inside the browser process, which is perhaps the most sophisticated software on a machine, and then groping around to find these tokens. It definitely is possible in some cases but it's likely to be pretty hard.
I'd compare it to the difference between stealing a person's credit card from a bag they left under their seat versus reaching under somebody's shirt to take the money they've tucked into their bra. I don't doubt that somebody, somewhere, is good enough to get away with that second one unnoticed, but I know for sure the first one is easier.