You'll mostly get altruistic and/or theoretical answers, like that all employees should have equity on principle, execs should on principle, or that it motivates execs to deliver results. I'll give you a practical answer: it's a compensation agreement.

There's no right or wrong answer what should or shouldn't be part of compensation, nor how much. 0% isn't any more or less "correct" than 2% or 0.2% or 20%.

If you don't like your compensation, negotiate harder. In your case, it sounds like you perceive the pay is already lower than you could get elsewhere, so there's not much of a trade to give. Basically, you believe you're worth a lot more than the company does, and also, it's personally important to you that you have equity in the company. That's fine. Either tell them that (and be ready to move on - there's probably not a satisfactory outcome), or simply accept that the parties disagree on how valuable this role is and move on.