From casual observation it appears that spouses who aren't introduced by mutual friends rarely like their spouse's friends. Friendships take time, are valued because of shared past experiences, and require a certain personality alignment to be sustained.

Also when spouses go and spend time with the other spouse's friends, its challenging to simultaneously catch-up with their old friends while also trying to include their new spouse in the conversation.

Some married couples work through this but others just privately and repeatedly criticize each other's friends so eventually they are left with only one friend -- their spouse.