Yes, indeed a very good point. Mine have been there for every birthday and we get Christmas with them every other year, but it is still very hard.
As a side note, also, you will find that in-laws might have different expectations of being a grandparent/aunt/uncle than your own families (though I think this has to do with a lot of factors). No one on my husband's side bathes, changes nappies, really sits down to play or anything with the children. My sisters bathe, change, play with and have the same awe and wonderment over them as we do.
My MIL told us once that she would only watch our daughter after we put her to bed. She also then said she wouldn't like to watch both of them at the same time (when number 2 came along). Well, we stopped asking her for any help at all and now we get comments like "I would like to take MY granddaughter out" (as if we were keeping them from her) ....can't win with some people.
I've had a British friend (married to a Brit as well) whose in-laws would leave the child in a messy nappy for hours until they came home. Some grandparents are wonderful here, tho, I know they provide most of the child care when the parents work. That has got to be really nice to have around.
I guess at least mine don't interfere in a controlling way.