Similarly, business people don’t take shit like this seriously until lawyers are involved. They see no evidence of your ability to actually hold them to account and so believe they can just push you around.
Hiring a professional who knows how to actually hold the other side legally accountable, or make them hurt (tens of thousands of bucks in lawyer fees and months down the drain if the case goes to court) shows you mean business.
Otherwise it’s just talk.
A lawyer is also an expert and can give expert advice, both strategic (what should we do?) and tactical (how do we do it?) based on knowledge and experience. Exactly the same way you do in your technical domain. Would you want advice from a non-engineer on how to architect or build something? What database to use? No.
Like developers, lawyers cost money for a reason, and it’s because of the value they can bring.