As to the "packed off with grandparents" comment - I agree with TheLouise.
My grandparents cared for us frequently on weekends whether or not my parents were traveling, because spending Saturday night with them was a huge treat! My grandfather was in poor health so not very active (he and my dad both became parents in middle age so Grampy was older than may have been the norm relative to our ages) - but he would talk with us and tell us about his childhood and youth - he was born in Bristol but ran away from home and ended up in Canada and then the U.S. after numerous adventures.
My grandma was the kindest person imaginable and we learned all sorts of things from her, she encouraged our creativity, our love of animals and nature and gardening, and was a wonderful example of a caring and sweet person. And her mild "wild side" of going to bingo showed us it's OK to have self-indulgent fun once in a while.
Similarly we used to stay weekends with my mother's younger sisters who were in full bell-bottom, purple VW bug flower power mode in the late 60s and early 70s, they took us to visit their own friends, bought us kooky clothes and styled our hair, and had popcorn/Coke parties on the floor of my (other) grandma's living room to watch special movies with us. And occasionally we stayed with mom's older sister who had a lovely home and was sophisticated and instilled in me a real love of antiques and home decorating and the art of entertaining and doing it all elegantly on a slim budget.
My parents were very loving and kind but they were not bold or adventuresome like Gramp or my young aunts, so it was good for us to have exposure to people who were less staid and security-oriented. They weren't interested in pets, gardening, bingo, antiques or teaching us about hair/makeup so those are just a few of the items we would not have been exposed to should we have never stayed with relatives or family friends.
My point is that parents truly are kidding themselves if they think only THEY have something to give/teach their children. It really stunts a child if they only have one input, one adult role model. The kids my heart breaks for are the ones who smugly pronounce "We haven't had a night away since little Ewan and Maisie were born, and that will be ten years next month," or some such claptrap. Poor Ewan and Maisie, I always think.