I don't favor single return per function myself, but in C code bases where that was the norm, I liked being able to add a debug print in one place which logs the return value.

  DEBUG("%s (%s) -> %d", __func__, str_arg, ret);
  return ret;

Single return doesn't necessarily mean nested ifs; it can be linear.

  bool success = true;

  if (condition(arg1)) {
    success = try_that(arg2);
  }

  if (success && condition2(arg3)) {
    success = other_thing(arg2);
  }

  ...

  return success;

Resource acquisition:

  widget_t *w = widget_create(arg);
  gadget_t *g = w ? gadget_create(w, arg2) : 0;
  char *gncopy = g ? strdup(gadget_name(g));

  if (gncopy) {
    // we must have g and w */
  }

Early returns can cause bugs; they can be premature. The coder though that if a certain condition is true, none of the other cases matter. And may be that was true, but now some of the cases (perhaps new ones) do matter. Someone wrote code to handle them, but didn't notice it's not reached because of that early return.