> If you don't use process isolation, every task can overwrite the heap and stack of every other running task We have a lot of modern languages that are memory

> If you don't use process isolation, every task can overwrite the heap and stack of every other running task We have a lot of modern languages that are memory safe at least in theory. However quite a few rely on the OS using these safety features in the background. For example the Java Runtime uses segfaults to catch null pointers instead of actively checking for them, at least as far as I remember.