Gay breakups usually do not involve any asset splitting, divorce lawyers and if there is some mud slinging around, the guys usually tend to keep the drama in check. Relatively few gay guys are fighting over who's gonna keep the children and who's gonna have visitation rights, etc.
A few gay couples grow apart. The guys recognize this, and choose to part amicably. They may have been friends before and choose to stay friends afterwards. Your typical gay dude has had a few FwB, FBs, BFs, and possibly quite a few guys who are somewhere in-between those popular categories. A few of those guys simply become lifelong friends.
Enters a new BF! Sure, the rules change somewhat. But you cannot really ask your BF to chuck all of his past AND all of his support network overboard. It would be very foolish to ask, and he would be even more foolish to agree to it.
You agree on the new rules of engagement and the life just gets a bit better and easier for everyone.
Say, you are a couple now. If anyone invites one of you he must know that the invitation is meant for both of you! You are an item.
You plan your time together. There are times when both of you want to socialize with both his and your friends. And there are times that are reserved for the two of you only. There are trips that you take with your friends together. And there are journeys that you take as a couple alone.
Good relationships are based on reciprocal trust. If you fear that your BF is cheating on you possibly with one of his buddies, do not even consider starting anything serious with the guy. Why waste your time with someone whom you do not trust, to start with?
Last but not least, starting to seriously date a guy is really not limited to his looks, money, endowment, etc., only. Like it or not, you are letting a new person into your life, together with his friends, possibly his family, his professional and personal networks, etc. True, the two of you may choose to filter away some and let the others in to a degree. But you are never going to be dating just one single, sole individual who has no links, no roots, no past, no history, no friends, no family.
I have had several valuable friends for quite a few years now. They stood by my side through the proverbial thick and thin. At times, their help and support mattered substantially. I will never forget this. And I cannot see how could anyone part ways with such people for the sake of a relationship with someone you may have met and have been dating for say, several months now?