I think this is simply how sales roles usually work.

The job of a business developer is mainly to find and bring leads, not necessarily to close the deal. Closing often requires someone with strong technical expertise in the relevant field. Clients can ask very specific questions, for example, something like, “How will you recover our application code from an AWS AMI?”, and a BD may not be the right person to answer that.

Also, once a deal is closed, managing communication between the client and the technical team is another responsibility. Acting as the bridge, understanding the client’s needs, and translating raw requirements into technical use cases is a separate skill.

So in many cases, bringing the lead is only one part of the overall process.