Luckily for me, I'm living in the same first house I bought straight out of grad school, 18 years and counting. All I ever wanted growing up was a sense of permanence. I am thankfully now able to provide that for myself physically. However, in terms of human relationships it's still a struggle, especially on the romantic side. The only person I can truly consider a "long term" friend is a fellow diplomat brat I met in Costa Rica. Even then we've had about a decade where we weren't in touch much. But I think we both recognize that there are very few people who "get" what it's like to have the types of parents we had, so we can bond over that.

I'm not sure that's unique to military, diplomacy, or other itinerant careers. Staying in the same place but switching jobs every 2-4 years can have the same impact, especially when it comes to "feeling the itch to move on." I think of this often in the context of my grandparents, who worked for the same companies/institutions for their entire careers.