If grandparents went on strike, we would all be sunk
When you reach the age of 65 or so, you fancy you've earned the right to put your feet up and relax. Your children are probably raised. You've paid off the mortgage. You've finished your career. The nest might be empty.
If you still have your health, you have about 15 years before old age really begins to take its toll. That's a long time in which to pursue those hobbies and pastimes you could previously only fitted in between everything else.
But life rarely works out quite as you plan. Suddenly you find that you're having to look after your grandchildren, and not just on the occasional weekend or evening but every working day.