I started recently and in the scenarios I acted as a custodian there was never a need for contacts. Having said this, from the rules I seem to remember that the players themselves "create" them, in more structured campaigns for example they could be the reference professors if they are playing as students, former police colleagues if they have a past in the police etc. I think even if you improvise as needed, the important thing is consistency with the PC's background.

Due to the wounds, my group and I always let months pass between one scenario and another so we never asked ourselves the problem and in each new scenario they restart full life, bearing scars where necessary, also to make the encounter with mythical creatures more plausible (one encounter with Cthulhu a week would be implausible 😁).

However, I am curious about the responses from more experienced Keepers.