I believe a major factor in this was a ruling by the Hoge Raad that a "free" phone with a contract is unlawful and is actually a loan. Carriers now have to list the price for the phone and for the service separately, so it's a lot more clear what the costs of the phone are.
Also, a "free" phone is now registered as a loan with monthly recurring costs, which impacts for example the maximum mortgage you can get on a home.
Sounds pretty similar to me and my grandparents, especially the part about not being vulnerable with each other. Mostly it's surface-level talks. For example, my grandpa is into plants and gardening, so we might talk about the garden or his most recent visit to the garden center or something.
And I'm pretty sure behavior like this is passed down through generations.