What is the purpose of a warm call?

I usually connect with clients via email, and those who show interest typically respond. After receiving a reply, I’m unsure of my next steps. I typically hop on a call to discuss the position in more detail and then bring up my fees. I’ve come across advice suggesting that I should identify their pain points and explain how I can address them. However, I’ve noticed that even when clients express interest, they often don’t follow through or sign the contract. While I understand that it’s a numbers game, I’m puzzled as to why someone would take the time to speak with a recruiter—indicating they work with agencies and need assistance—only to ultimately decline to sign once the contract is sent.

I feel there may be something I’m missing in this process, and I would greatly appreciate any insights or advice from others. Thank you!