In typography there are ligatures that exist because they help readability (ex: ff fi tt) and others that are pure ornamental (ex: st).
Personaly I see coding ligatures as ornamental as I can't read === faster if all the lines are merged because I need a precision in the meaning of this symbols that I wouldn't need if I was reading text where I can use, - – — (minus, en dash, em dash) and while it might look a little off no one would lost the intended meaning.
Most of today's coding ligatures merge === such that it has three lines vertically as opposed to just two (evoking a "hamburger menu" icon as others have noted), in addition it's also generally still three character widths versus two. I find it easier to visually spot the difference between the == and === ligatures in Fira Code or Cascadia Code than between the non-ligature forms and counting the spaces in between the lines. Your mileage may vary of course, but in most cases after several years with Fira Code I find the ligatures in general are much faster for "at a glance" precision than some of the non-ligature forms.
