There’s a huge difference between once a year and zero. Think of the strong traditions behind birthday or annual holiday greetings, for instance.
Look at it this way. Let’s say you reach out to 100 people once a year. Well there are 7.7 billion people on Earth. You’re putting those 100 people into your 99.999999 percentile for that year!
I'm friends with someone in college. We graduate and move to separate cities. We go from regular contact to every few months. By 2 or 3 years from graduation its just a text on birthdays. That last for a year or two. We both get married and then reconnect because of X. We become closer friends again.
That same situation is less likely to happen without the yearly contact. At the very least the friendship is maintained, even if the maintaining can only last a few years before deteriorating, and it gives the relationship a higher chance to pick back up at a later date.
Look at it this way. Let’s say you reach out to 100 people once a year. Well there are 7.7 billion people on Earth. You’re putting those 100 people into your 99.999999 percentile for that year!