While it's true that marriage and wedding ceremonies are widespread across cultures, it's not accurate to say that every single culture in the world has them. There are some societies and subcultures where marriage as we commonly understand it doesn't exist, or where formal wedding ceremonies are not practiced.

Here are a few examples of cultures or groups where traditional marriage and wedding ceremonies may be different or absent:

1. Some nomadic or hunter-gatherer societies have less formal unions or no concept of marriage as an institution.

2. Certain indigenous groups may have unique customs around relationships that don't necessarily involve Western-style weddings.

3. Some modern secular or non-religious communities may choose not to have formal ceremonies.

4. In matriarchal societies, marriage customs can differ significantly from patriarchal traditions.

5. Certain religious orders or monastic communities take vows of celibacy and don't practice marriage.

6. Some polyamorous groups may not follow traditional marriage structures.

That said, most major cultural groups do have some form of recognized partnership or ceremony related to forming long-term relationships. The specifics vary widely across the globe.

It's important to approach this topic with cultural sensitivity and recognize the diversity of human social structures and practices worldwide.