Yes, it's one of my hobbies however I didn't find new friends because of it but I became interested in postcrossing because of some of my friends who don't live with me in the same country/city
That happenned when I found a couple of people in net with the same interests in music, we had often long chats about everything and later became very good friends, at least as much as it was possible in such virtual format. And from that time we started to make exchanged with postcards and even small gifts, it was always such a pleasure for the both sides!
I also like postcrossing because one of my hobbies is quilling and I can make different handmade postcards for it, however I rather often buy the ready ones with interesting design or connected with special holidays like valentines day postcards https://masterbundles.com/valentines-day-postcards/
too. It's also a good choice in my case for postcrossing with totally unknown people for me, yeah I had such experience too but it's more interesting when you already know each other.