No one's making them do it, but just because they stop doesn't mean others will. Pausing just means they give up control. It's like asking the US to unilaterally disarm -- it just guarantees that the less scrupulous groups win.
Anthropic is explicitly calling for a coordinated pause: https://www.reuters.com/business/anthropic-says-ai-labs-need... Maybe this is a lie, but the way to call their bluff is to push on competitors to agree.